[Doc] Minor: Fixes several formatting issues
[Doc] Minor: Fixes several formatting issues

Fixes several minor formatting issues in the [Continuous Compilation] [1] section.

[1]: http://spark.apache.org/docs/latest/building-spark.html#continuous-compilation

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Author: Cheng Lian <lian@databricks.com>

Closes #4316 from liancheng/fix-build-instruction-docs and squashes the following commits:

0a92e01 [Cheng Lian] Fixes several formatting issues

darionyaphet/spark,srowen/spark,jkbradley/spark,lvdongr/spark,publicRoman/spark,panfengfeng/spark,apache-spark-on-k8s/spark,gengliangwang/spark,guoxiaolongzte/spark,hvanhovell/spark,chuckchen/spark,wzhfy/spark,gengliangwang/spark,stanzhai/spark,gioenn/xSpark,cin/spark,sachintyagi22/spark,liyichao/spark,darionyaphet/spark,JerryLead/spark,bOOm-X/spark,apache-spark-on-k8s/spark,michalsenkyr/spark,brad-kaiser/spark,janewangfb/spark,sachintyagi22/spark,hhbyyh/spark,zuotingbing/spark,goldmedal/spark,SnappyDataInc/spark,srowen/spark,sahilTakiar/spark,SHASHANKB/spark,mahak/spark,narahari92/spark,bravo-zhang/spark,tengpeng/spark,ioana-delaney/spark,wangyum/spark,srowen/spark,saltstar/spark,MLnick/spark,rekhajoshm/spark,zuotingbing/spark,saturday-shi/spark,apache/spark,mzl9039/spark,goldmedal/spark,1haodian/spark,szhem/spark,eyalfa/spark,pgandhi999/spark,taroplus/spark,LantaoJin/spark,jiangxb1987/spark,bdrillard/spark,alunarbeach/spark,shuangshuangwang/spark,darionyaphet/spark,kimoonkim/spark,haowu80s/spark,jkbradley/spark,maropu/spark,sureshthalamati/spark,eyalfa/spark,bOOm-X/spark,andrewor14/spark,taroplus/spark,JoshRosen/spark,1haodian/spark,HyukjinKwon/spark,aosagie/spark,michalsenkyr/spark,wangmiao1981/spark,Panos-Bletsos/spark-cost-model-optimizer,akopich/spark,stanzhai/spark,hvanhovell/spark,HyukjinKwon/spark,wangmiao1981/spark,andrewor14/spark,ddna1021/spark,publicRoman/spark,spark-test/spark,nilsgrabbert/spark,adrian-ionescu/apache-spark,zzcclp/spark,loneknightpy/spark,Aegeaner/spark,jkbradley/spark,ddna1021/spark,pgandhi999/spark,dongjoon-hyun/spark,hhbyyh/spark,rezasafi/spark,techaddict/spark,WindCanDie/spark,goldmedal/spark,rezasafi/spark,ibm-research-ireland/sparkoscope,ptkool/spark,jrshust/spark,jrshust/spark,guoxiaolongzte/spark,vinodkc/spark,wangmiao1981/spark,milliman/spark,shuangshuangwang/spark,poffuomo/spark,wangmiao1981/spark,map222/spark,gioenn/xSpark,joseph-torres/spark,rekhajoshm/spark,LantaoJin/spark,map222/spark,zzcclp/spark,aokolnychyi/spark,facaiy/spark,cloud-fan/spark,ConeyLiu/spark,jkbradley/spark,apache-spark-on-k8s/spark,dongjoon-hyun/spark,jiangxb1987/spark,milliman/spark,saltstar/spark,ahnqirage/spark,janewangfb/spark,pronix/spark,mahak/spark,rikima/spark,LantaoJin/spark,bravo-zhang/spark,big-pegasus/spark,dhruve/spark,shaneknapp/spark,wangyum/spark,hvanhovell/spark,markhamstra/spark,skonto/spark,1haodian/spark,bdrillard/spark,someorz/spark,actuaryzhang/spark,SHASHANKB/spark,liutang123/spark,UndeadBaneGitHub/spark,chuckchen/spark,mdespriee/spark,SnappyDataInc/spark,panfengfeng/spark,pronix/spark,lxsmnv/spark,aokolnychyi/spark,shubhamchopra/spark,gioenn/xSpark,someorz/spark,sahilTakiar/spark,caneGuy/spark,nilsgrabbert/spark,brad-kaiser/spark,janewangfb/spark,esi-mineset/spark,JoshRosen/spark,nlalevee/spark,saturday-shi/spark,zzcclp/spark,patrick-nicholson/spark,stanzhai/spark,zuotingbing/spark,jiangxb1987/spark,liyichao/spark,publicRoman/spark,wangyum/spark,akopich/spark,liutang123/spark,setjet/spark,icexelloss/spark,mdespriee/spark,icexelloss/spark,debugger87/spark,cin/spark,zero323/spark,bravo-zhang/spark,ron8hu/spark,srowen/spark,zero323/spark,akopich/spark,saturday-shi/spark,rednaxelafx/apache-spark,jianran/spark,wzhfy/spark,xuanyuanking/spark,aokolnychyi/spark,actuaryzhang/spark,adrian-ionescu/apache-spark,adrian-ionescu/apache-spark,jkbradley/spark,spark-test/spark,Panos-Bletsos/spark-cost-model-optimizer,pgandhi999/spark,kimoonkim/spark,skonto/spark,jlopezmalla/spark,wzhfy/spark,JerryLead/spark,liutang123/spark,alunarbeach/spark,xuanyuanking/spark,ron8hu/spark,michalsenkyr/spark,aray/spark,cloud-fan/spark,bOOm-X/spark,skonto/spark,someorz/spark,nchammas/spark,UndeadBaneGitHub/spark,ptkool/spark,actuaryzhang/spark,jiangxb1987/spark,esi-mineset/spark,jrshust/spark,ericvandenbergfb/spark,andrewor14/spark,mzl9039/spark,highfei2011/spark,dongjoon-hyun/spark,sureshthalamati/spark,LantaoJin/spark,debugger87/spark,sureshthalamati/spark,xflin/spark,milliman/spark,nlalevee/spark,big-pegasus/spark,michalsenkyr/spark,publicRoman/spark,xflin/spark,wzhfy/spark,LantaoJin/spark,chuckchen/spark,actuaryzhang/spark,kimoonkim/spark,loneknightpy/spark,techaddict/spark,1haodian/spark,cin/spark,SHASHANKB/spark,ajaysaini725/spark,wangyum/spark,shaneknapp/spark,bdrillard/spark,andrewor14/iolap,ahnqirage/spark,szhem/spark,ahnqirage/spark,debugger87/spark,shaneknapp/spark,ahnqirage/spark,maropu/spark,bOOm-X/spark,highfei2011/spark,andrewor14/iolap,taroplus/spark,map222/spark,BryanCutler/spark,metamx/spark,szhem/spark,jlopezmalla/spark,kissmetrics/spark,skonto/spark,Aegeaner/spark,aosagie/spark,aray/spark,hvanhovell/spark,lvdongr/spark,WeichenXu123/spark,stanzhai/spark,JoshRosen/spark,metamx/spark,poffuomo/spark,rednaxelafx/apache-spark,haowu80s/spark,mahak/spark,joseph-torres/spark,apache-spark-on-k8s/spark,jianran/spark,rekhajoshm/spark,loneknightpy/spark,debugger87/spark,ddna1021/spark,nchammas/spark,zuotingbing/spark,spark-test/spark,chuckchen/spark,hvanhovell/spark,darionyaphet/spark,saltstar/spark,l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