[SPARKR][MINOR] Fix LDA doc
[SPARKR][MINOR] Fix LDA doc

## What changes were proposed in this pull request?

This PR tries to fix the name of the `SparkDataFrame` used in the example. Also, it gives a reference url of an example data file so that users can play with.

## How was this patch tested?

Manual test.

Author: Junyang Qian <junyangq@databricks.com>

Closes #14853 from junyangq/SPARKR-FixLDADoc.

alunarbeach/spark,JerryLead/spark,nlalevee/spark,SnappyDataInc/spark,joseph-torres/spark,aosagie/spark,UndeadBaneGitHub/spark,setjet/spark,zhouyejoe/spark,janewangfb/spark,poffuomo/spark,esi-mineset/spark,andrewor14/spark,Aegeaner/spark,akopich/spark,bdrillard/spark,sahilTakiar/spark,big-pegasus/spark,publicRoman/spark,debugger87/spark,big-pegasus/spark,esi-mineset/spark,michalsenkyr/spark,jiangxb1987/spark,kissmetrics/spark,apache-spark-on-k8s/spark,ueshin/apache-spark,zuotingbing/spark,liutang123/spark,SnappyDataInc/spark,nilsgrabbert/spark,bOOm-X/spark,kevinyu98/spark,big-pegasus/spark,Panos-Bletsos/spark-cost-model-optimizer,minixalpha/spark,ahnqirage/spark,darionyaphet/spark,minixalpha/spark,bravo-zhang/spark,byakuinss/spark,dbtsai/spark,dongjoon-hyun/spark,JoshRosen/spark,markhamstra/spark,patrick-nicholson/spark,MLnick/spark,mdespriee/spark,joseph-torres/spark,someorz/spark,shuangshuangwang/spark,esi-mineset/spark,lxsmnv/spark,stanzhai/spark,apache/spark,saturday-shi/spark,apache-spark-on-k8s/spark,holdenk/spark,map222/spark,tejasapatil/spark,BryanCutler/spark,kimoonkim/spark,kiszk/spark,rekhajoshm/spark,zero323/spark,ueshin/apache-spark,jrshust/spark,byakuinss/spark,chuckchen/spark,mzl9039/spark,andrewor14/spark,lvdongr/spark,joseph-torres/spark,apache/spark,bravo-zhang/spark,lxsmnv/spark,wzhfy/spark,ptkool/spark,adrian-ionescu/apache-spark,dbtsai/spark,szhem/spark,highfei2011/spark,SnappyDataInc/spark,janewangfb/spark,huang1900/spark,yanboliang/spark,lxsmnv/spark,techaddict/spark,Aegeaner/spark,brad-kaiser/spark,nchammas/spark,apache-spark-on-k8s/spark,aokolnychyi/spark,aosagie/spark,kissmetrics/spark,sureshthalamati/spark,shaneknapp/spark,gengliangwang/spark,zhouyejoe/spark,minixalpha/spark,someorz/spark,milliman/spark,ptkool/spark,brad-kaiser/spark,icexelloss/spark,shuangshuangwang/spark,nchammas/spark,loneknightpy/spark,ptkool/spark,tejasapatil/spark,aokolnychyi/spark,dongjoon-hyun/spark,BryanCutler/spark,pgandhi999/spark,facaiy/spark,panfengfeng/spark,actuaryzhang/spark,ConeyLiu/spark,shaneknapp/spark,ajaysaini725/spark,saturday-shi/spark,kissmetrics/spark,skonto/spark,aray/spark,panfengfeng/spark,jiangxb1987/spark,janewangfb/spark,actuaryzhang/spark,hvanhovell/spark,janewangfb/spark,cloud-fan/spark,WindCanDie/spark,goldmedal/spark,highfei2011/spark,setjet/spark,dhruve/spark,kimoonkim/spark,ueshin/apache-spark,aray/spark,witgo/spark,kiszk/spark,ddna1021/spark,dongjoon-hyun/spark,map222/spark,hvanhovell/spark,shuangshuangwang/spark,janewangfb/spark,spark-test/spark,MLnick/spark,rezasafi/spark,Panos-Bletsos/spark-cost-model-optimizer,Aegeaner/spark,zhouyejoe/spark,jrshust/spark,guoxiaolongzte/spark,loneknightpy/spark,techaddict/spark,nilsgrabbert/spark,ueshin/apache-spark,aray/spark,actuaryzhang/spark,gengliangwang/spark,ahnqirage/spark,narahari92/spark,JoshRosen/spark,nchammas/spark,ericvandenbergfb/spark,patrick-nicholson/spark,ericvandenbergfb/spark,Aegeaner/spark,ajaysaini725/spark,wangyum/spark,ajaysaini725/spark,ahnqirage/spark,jiangxb1987/spark,saltstar/spark,saltstar/spark,tengpeng/spark,michalsenkyr/spark,facaiy/spark,1haodian/spark,1haodian/spark,rekhajoshm/spark,MLnick/spark,wzhfy/spark,highfei2011/spark,aosagie/spark,michalsenkyr/spark,poffuomo/spark,stanzhai/spark,jiangxb1987/spark,liyichao/spark,LantaoJin/spark,metamx/spark,nchammas/spark,sachintyagi22/spark,WeichenXu123/spark,liyichao/spark,highfei2011/spark,ConeyLiu/spark,MLnick/spark,szhem/spark,ajaysaini725/spark,saturday-shi/spark,joseph-torres/spark,cin/spark,tejasapatil/spark,techaddict/spark,aokolnychyi/spark,minixalpha/spark,witgo/spark,bdrillard/spark,bOOm-X/spark,HyukjinKwon/spark,jlopezmalla/spark,Panos-Bletsos/spark-cost-model-optimizer,darionyaphet/spark,someorz/spark,xflin/spark,apache/spark,patrick-nicholson/spark,dhruve/spark,pgandhi999/spark,sachintyagi22/spark,shubhamchopra/spark,ron8hu/spark,rikima/spark,alunarbeach/spark,apache-spark-on-k8s/spark,ron8hu/spark,ddna1021/spark,cin/spark,liyichao/spark,SHASHANKB/spark,rednaxelafx/apache-spark,rekhajoshm/spark,map222/spark,srowen/spark,map222/spark,sahilTakiar/spark,holdenk/spark,zhouyejoe/spark,mahak/spark,bOOm-X/spark,sahilTakiar/spark,jianran/spark,ajaysaini725/spark,publicRoman/spark,ron8hu/spark,chuckchen/spark,rednaxelafx/apache-spark,kissmetrics/spark,szhem/spark,jiangxb1987/spark,maropu/spark,goldmedal/spark,joseph-torres/spark,WeichenXu123/spark,hhbyyh/spark,holdenk/spark,markhamstra/spark,sureshthalamati/spark,shubhamchopra/spark,huang1900/spark,lxsmnv/spark,szhem/spark,mzl9039/spark,techaddict/spark,tengpeng/spark,tejasapatil/spark,nilsgrabbert/spark,bravo-zhang/spark,jkbradley/spark,HyukjinKwon/spark,zzcclp/spark,maropu/spark,spark-test/spark,aokolnychyi/spark,sureshthalamati/spark,alunarbeach/spark,wzhfy/spark,JerryLead/spark,nchammas/spark,caneGuy/spark,esi-mineset/spark,zero323/spark,ptkool/spark,hvanhovell/spark,adrian-ionescu/apache-spark,tengpeng/spark,taroplus/spark,map222/spark,big-pegasus/spark,loneknightpy/spark,huang1900/spark,markhamstra/spark,mike0sv/spark,srowen/spark,ibm-research-ireland/sparkoscope,LantaoJin/spark,LantaoJin/spark,srowen/spark,shubhamchopra/spark,SHASHANKB/spark,actuaryzhang/spark,andrewor14/spark,ibm-research-ireland/sparkoscope,holdenk/spark,1haodian/spark,michalsenkyr/spark,ConeyLiu/spark,akopich/spark,mike0sv/spark,srowen/spark,ericvandenbergfb/spark,nlalevee/spark,ddna1021/spark,jiangxb1987/spark,ConeyLiu/spark,jkbradley/spark,highfei2011/spark,actuaryzhang/spark,setjet/spark,ron8hu/spark,jrshust/spark,aosagie/spark,zuotingbing/spark,WindCanDie/spark,aray/spark,JerryLead/spark,hhbyyh/spark,lxsmnv/spark,aray/spark,ibm-research-ireland/sparkoscope,lvdongr/spark,apache/spark,wzhfy/spark,spark-test/spark,chuckchen/spark,saturday-shi/spark,shuangshuangwang/spark,kevinyu98/spark,janewangfb/spark,lvdongr/spark,wangyum/spark,adrian-ionescu/apache-spark,zzcclp/spark,ddna1021/spark,eyalfa/spark,jiangxb1987/spark,byakuinss/spark,eyalfa/spark,highfei2011/spark,mahak/spark,vinodkc/spark,jrshust/spark,publicRoman/spark,nilsgrabbert/spark,vinodkc/spark,kevinyu98/spark,sureshthalamati/spark,sachintyagi22/spark,nilsgrabbert/spark,bdrillard/spark,zzcclp/spark,joseph-torres/spark,jlopezmalla/spark,rikima/spark,rekhajoshm/spark,zhouyejoe/spark,witgo/spark,ConeyLiu/spark,big-pegasus/spark,guoxiaolongzte/spark,goldmedal/spark,taroplus/spark,ptkool/spark,tengpeng/spark,spark-test/spark,shubhamchopra/spark,bOOm-X/spark,tejasapatil/spark,ddna1021/spark,chuckchen/spark,cloud-fan/spark,goldmedal/spark,gengliangwang/spark,bravo-zhang/spark,ueshin/apache-spark,caneGuy/spark,stanzhai/spark,zuotingbing/spark,tengpeng/spark,MLnick/spark,mahak/spark,zzcclp/spark,zzcclp/spark,hvanhovell/spark,someorz/spark,adrian-ionescu/apache-spark,skonto/spark,loneknightpy/spark,brad-kaiser/spark,chuckchen/spark,poffuomo/spark,loneknightpy/spark,pgandhi999/spark,UndeadBaneGitHub/spark,apache-spark-on-k8s/spark,taroplus/spark,icexelloss/spark,cloud-fan/spark,esi-mineset/spark,Panos-Bletsos/spark-cost-model-optimizer,debugger87/spark,icexelloss/spark,SnappyDataInc/spark,milliman/spark,zuotingbing/spark,dhruve/spark,rekhajoshm/spark,poffuomo/spark,jianran/spark,byakuinss/spark,minixalpha/spark,LantaoJin/spark,ioana-delaney/spark,wangmiao1981/spark,adrian-ionescu/apache-spark,patrick-nicholson/spark,lvdongr/spark,caneGuy/spark,akopich/spark,UndeadBaneGitHub/spark,bdrillard/spark,stanzhai/spark,jlopezmalla/spark,gengliangwang/spark,shaneknapp/spark,JerryLead/spark,BryanCutler/spark,ioana-delaney/spark,cin/spark,mike0sv/spark,1haodian/spark,wangmiao1981/spark,jkbradley/spark,debugger87/spark,zero323/spark,saturday-shi/spark,vinodkc/spark,setjet/spark,nchammas/spark,zuotingbing/spark,sureshthalamati/spark,nilsgrabbert/spark,liyichao/spark,eyalfa/spark,maropu/spark,kiszk/spark,guoxiaolongzte/spark,eyalfa/spark,joseph-torres/spark,someorz/spark,eyalfa/spark,BryanCutler/spark,shubhamchopra/spark,JoshRosen/spark,ueshin/apache-spark,markhamstra/spark,ericvandenbergfb/spark,debugger87/spark,goldmedal/spark,WindCanDie/spark,mahak/spark,rikima/spark,tejasapatil/spark,yanboliang/spark,poffuomo/spark,1haodian/spark,kevinyu98/spark,apache-spark-on-k8s/spark,ptkool/spark,mike0sv/spark,huang1900/spark,mike0sv/spark,panfengfeng/spark,brad-kaiser/spark,mdespriee/spark,jkbradley/spark,dhruve/spark,someorz/spark,facaiy/spark,techaddict/spark,ddna1021/spark,ron8hu/spark,cin/spark,stanzhai/spark,shaneknapp/spark,saltstar/spark,xuanyuanking/spark,taroplus/spark,narahari92/spark,narahari92/spark,kevinyu98/spark,mahak/spark,andrewor14/spark,wangmiao1981/spark,darionyaphet/spark,gengliangwang/spark,akopich/spark,xflin/spark,xuanyuanking/spark,ptkool/spark,ahnqirage/spark,BryanCutler/spark,JerryLead/spark,UndeadBaneGitHub/spark,esi-mineset/spark,esi-mineset/spark,nlalevee/spark,goldmedal/spark,skonto/spark,milliman/spark,spark-test/spark,michalsenkyr/spark,rikima/spark,xflin/spark,dhruve/spark,saturday-shi/spark,zuotingbing/spark,aray/spark,metamx/spark,mdespriee/spark,milliman/spark,SnappyDataInc/spark,nlalevee/spark,milliman/spark,michalsenkyr/spark,wangyum/spark,wzhfy/spark,apache/spark,rikima/spark,WeichenXu123/spark,MLnick/spark,JerryLead/spark,zhouyejoe/spark,icexelloss/spark,kiszk/spark,caneGuy/spark,akopich/spark,lvdongr/spark,aokolnychyi/spark,cloud-fan/spark,srowen/spark,icexelloss/spark,rednaxelafx/apache-spark,wangmiao1981/spark,setjet/spark,mdespriee/spark,setjet/spark,jlopezmalla/spark,yanboliang/spark,wangyum/spark,aosagie/spark,spark-test/spark,mahak/spark,akopich/spark,SHASHANKB/spark,sahilTakiar/spark,holdenk/spark,WindCanDie/spark,byakuinss/spark,zhouyejoe/spark,hvanhovell/spark,SHASHANKB/spark,pgandhi999/spark,tejasapatil/spark,mdespriee/spark,dongjoon-hyun/spark,rednaxelafx/apache-spark,szhem/spark,ron8hu/spark,Panos-Bletsos/spark-cost-model-optimizer,sahilTakiar/spark,apache-spark-on-k8s/spark,LantaoJin/spark,guoxiaolongzte/spark,dongjoon-hyun/spark,minixalpha/spark,byakuinss/spark,bOOm-X/spark,michalsenkyr/spark,rezasafi/spark,bravo-zhang/spark,vinodkc/spark,ajaysaini725/spark,cloud-fan/spark,markhamstra/spark,zzcclp/spark,SHASHANKB/spark,kimoonkim/spark,jlopezmalla/spark,JoshRosen/spark,wangyum/spark,witgo/spark,alunarbeach/spark,brad-kaiser/spark,hvanhovell/spark,gengliangwang/spark,rekhajoshm/spark,publicRoman/spark,nilsgrabbert/spark,zero323/spark,alunarbeach/spark,brad-kaiser/spark,metamx/spark,hhbyyh/spark,narahari92/spark,nlalevee/spark,aosagie/spark,map222/spark,HyukjinKwon/spark,taroplus/spark,maropu/spark,kissmetrics/spark,hhbyyh/spark,caneGuy/spark,panfengfeng/spark,ConeyLiu/spark,darionyaphet/spark,JoshRosen/spark,JerryLead/spark,setjet/spark,maropu/spark,Aegeaner/spark,hvanhovell/spark,alunarbeach/spark,dhruve/spark,dbtsai/spark,facaiy/spark,BryanCutler/spark,debugger87/spark,srowen/spark,kimoonkim/spark,liutang123/spark,vinodkc/spark,apache/spark,BryanCutler/spark,vinodkc/spark,markhamstra/spark,skonto/spark,huang1900/spark,liutang123/spark,eyalfa/spark,shaneknapp/spark,andrewor14/spark,yanboliang/spark,loneknightpy/spark,markhamstra/spark,rezasafi/spark,jianran/spark,wangyum/spark,poffuomo/spark,guoxiaolongzte/spark,xuanyuanking/spark,shaneknapp/spark,aray/spark,saltstar/spark,wzhfy/spark,sachintyagi22/spark,someorz/spark,ioana-delaney/spark,brad-kaiser/spark,Aegeaner/spark,sachintyagi22/spark,xuanyuanking/spark,SHASHANKB/spark,rikima/spark,dbtsai/spark,xflin/spark,1haodian/spark,bdrillard/spark,shuangshuangwang/spark,ioana-delaney/spark,ioana-delaney/spark,darionyaphet/spark,publicRoman/spark,maropu/spark,tengpeng/spark,rikima/spark,ueshin/apache-spark,ddna1021/spark,kiszk/spark,witgo/spark,publicRoman/spark,sachintyagi22/spark,yanboliang/spark,cin/spark,dbtsai/spark,metamx/spark,rezasafi/spark,goldmedal/spark,lvdongr/spark,icexelloss/spark,gengliangwang/spark,lxsmnv/spark,sureshthalamati/spark,lxsmnv/spark,guoxiaolongzte/spark,pgandhi999/spark,HyukjinKwon/spark,stanzhai/spark,liyichao/spark,ericvandenbergfb/spark,mike0sv/spark,panfengfeng/spark,poffuomo/spark,holdenk/spark,rezasafi/spark,patrick-nicholson/spark,rezasafi/spark,yanboliang/spark,kimoonkim/spark,adrian-ionescu/apache-spark,map222/spark,saltstar/spark,zuotingbing/spark,andrewor14/spark,kissmetrics/spark,LantaoJin/spark,mdespriee/spark,stanzhai/spark,xflin/spark,mzl9039/spark,narahari92/spark,techaddict/spark,nlalevee/spark,WindCanDie/spark,ron8hu/spark,HyukjinKwon/spark,icexelloss/spark,loneknightpy/spark,patrick-nicholson/spark,ibm-research-ireland/sparkoscope,kevinyu98/spark,rednaxelafx/apache-spark,saltstar/spark,1haodian/spark,JoshRosen/spark,ahnqirage/spark,WeichenXu123/spark,wangmiao1981/spark,metamx/spark,pgandhi999/spark,hhbyyh/spark,jianran/spark,jianran/spark,yanboliang/spark,zero323/spark,facaiy/spark,mzl9039/spark,guoxiaolongzte/spark,jlopezmalla/spark,zzcclp/spark,WeichenXu123/spark,ahnqirage/spark,jrshust/spark,dbtsai/spark,cin/spark,ioana-delaney/spark,techaddict/spark,jlopezmalla/spark,liutang123/spark,UndeadBaneGitHub/spark,dongjoon-hyun/spark,jianran/spark,metamx/spark,wangmiao1981/spark,chuckchen/spark,ahnqirage/spark,hhbyyh/spark,cin/spark,andrewor14/spark,darionyaphet/spark,mzl9039/spark,matthewfranglen/spark,nlalevee/spark,bdrillard/spark,mahak/spark,mike0sv/spark,jkbradley/spark,SnappyDataInc/spark,szhem/spark,tengpeng/spark,JoshRosen/spark,dongjoon-hyun/spark,SHASHANKB/spark,chuckchen/spark,holdenk/spark,actuaryzhang/spark,ibm-research-ireland/sparkoscope,akopich/spark,bOOm-X/spark,rekhajoshm/spark,bravo-zhang/spark,panfengfeng/spark,zero323/spark,Panos-Bletsos/spark-cost-model-optimizer,jkbradley/spark,witgo/spark,rednaxelafx/apache-spark,sahilTakiar/spark,mdespriee/spark,narahari92/spark,ioana-delaney/spark,xuanyuanking/spark,shaneknapp/spark,cloud-fan/spark,wangmiao1981/spark,kevinyu98/spark,dbtsai/spark,jkbradley/spark,SnappyDataInc/spark,maropu/spark,saturday-shi/spark,actuaryzhang/spark,sahilTakiar/spark,MLnick/spark,alunarbeach/spark,big-pegasus/spark,minixalpha/spark,milliman/spark,ajaysaini725/spark,cloud-fan/spark,aokolnychyi/spark,rednaxelafx/apache-spark,kiszk/spark,debugger87/spark,kimoonkim/spark,skonto/spark,witgo/spark,kiszk/spark,darionyaphet/spark,facaiy/spark,huang1900/spark,xuanyuanking/spark,rezasafi/spark,liyichao/spark,xflin/spark,shuangshuangwang/spark,wangyum/spark,aosagie/spark,wzhfy/spark,highfei2011/spark,Panos-Bletsos/spark-cost-model-optimizer,liutang123/spark,bravo-zhang/spark,patrick-nicholson/spark,HyukjinKwon/spark,kimoonkim/spark,UndeadBaneGitHub/spark,skonto/spark,byakuinss/spark,vinodkc/spark,spark-test/spark,zero323/spark,bdrillard/spark,publicRoman/spark,WindCanDie/spark,ConeyLiu/spark,taroplus/spark,eyalfa/spark,panfengfeng/spark,UndeadBaneGitHub/spark,taroplus/spark,bOOm-X/spark,mzl9039/spark,saltstar/spark,narahari92/spark,liyichao/spark,ericvandenbergfb/spark,WindCanDie/spark,nchammas/spark,xuanyuanking/spark,HyukjinKwon/spark,szhem/spark,milliman/spark,shubhamchopra/spark,xflin/spark,hhbyyh/spark,shubhamchopra/spark,ibm-research-ireland/sparkoscope,pgandhi999/spark,ibm-research-ireland/sparkoscope,facaiy/spark,mzl9039/spark,kissmetrics/spark,srowen/spark,huang1900/spark,WeichenXu123/spark,debugger87/spark,metamx/spark,janewangfb/spark,sureshthalamati/spark,skonto/spark,jrshust/spark,liutang123/spark,jianran/spark,sachintyagi22/spark,liutang123/spark,caneGuy/spark,lvdongr/spark,dhruve/spark,apache/spark,LantaoJin/spark,shuangshuangwang/spark,caneGuy/spark,ericvandenbergfb/spark,Aegeaner/spark,adrian-ionescu/apache-spark,big-pegasus/spark,WeichenXu123/spark,jrshust/spark,aokolnychyi/spark