Update linear-regression.md (#9103)
Update linear-regression.md (#9103)

* Update linear-regression.md

Reduce number of epoch to 20, as validation accuracy doesn't improve any further.
Added assertion to check for achieved accuracy in preparation for tutorial regression.

* fixed location of assertion

moved assertion to correct location

szha/mxnet,mbaijal/incubator-mxnet,larroy/mxnet,vikingMei/mxnet,TuSimple/mxnet,weleen/mxnet,sxjscience/mxnet,reminisce/mxnet,dmlc/mxnet,yajiedesign/mxnet,ptrendx/mxnet,weleen/mxnet,indhub/mxnet,tlby/mxnet,ForkedReposBak/mxnet,sxjscience/mxnet,Northrend/mxnet,yajiedesign/mxnet,jamesliu/mxnet,jiajiechen/mxnet,precedenceguo/mxnet,Northrend/mxnet,vikingMei/mxnet,rahul003/mxnet,indhub/mxnet,mbaijal/incubator-mxnet,ykim362/mxnet,jennyzhang0215/incubator-mxnet,yuruofeifei/mxnet,yuruofeifei/mxnet,TuSimple/mxnet,jiajiechen/mxnet,fullfanta/mxnet,rahul003/mxnet,weleen/mxnet,weleen/mxnet,ykim362/mxnet,sxjscience/mxnet,yajiedesign/mxnet,apache/incubator-mxnet,leezu/mxnet,reminisce/mxnet,eric-haibin-lin/mxnet,tlby/mxnet,jennyzhang0215/incubator-mxnet,larroy/mxnet,Northrend/mxnet,rahul003/mxnet,jennyzhang0215/incubator-mxnet,ykim362/mxnet,LinkHS/incubator-mxnet,indhub/mxnet,jennyzhang0215/incubator-mxnet,szha/mxnet,CodingCat/mxnet,szha/mxnet,precedenceguo/mxnet,fullfanta/mxnet,reminisce/mxnet,fullfanta/mxnet,leezu/mxnet,CodingCat/mxnet,precedenceguo/mxnet,sxjscience/mxnet,navrasio/mxnet,sxjscience/mxnet,vikingMei/mxnet,tornadomeet/mxnet,dmlc/mxnet,luoyetx/mxnet,vikingMei/mxnet,Northrend/mxnet,luoyetx/mxnet,TuSimple/mxnet,ForkedReposBak/mxnet,leezu/mxnet,szha/mxnet,luoyetx/mxnet,jamesliu/mxnet,tornadomeet/mxnet,CodingCat/mxnet,leezu/mxnet,CodingCat/mxnet,tornadomeet/mxnet,ptrendx/mxnet,tornadomeet/mxnet,larroy/mxnet,zhreshold/mxnet,eric-haibin-lin/mxnet,tornadomeet/mxnet,zhreshold/mxnet,TuSimple/mxnet,LinkHS/incubator-mxnet,rahul003/mxnet,jiajiechen/mxnet,TuSimple/mxnet,navrasio/mxnet,Northrend/mxnet,jennyzhang0215/incubator-mxnet,navrasio/mxnet,ykim362/mxnet,dmlc/mxnet,rahul003/mxnet,mbaijal/incubator-mxnet,ptrendx/mxnet,yajiedesign/mxnet,dmlc/mxnet,weleen/mxnet,indhub/mxnet,reminisce/mxnet,eric-haibin-lin/mxnet,yuruofeifei/mxnet,ykim362/mxnet,rahul003/mxnet,Northrend/mxnet,ptrendx/mxnet,mbaijal/incubator-mxnet,vikingMei/mxnet,mbaijal/incubator-mxnet,precedenceguo/mxnet,sxjscience/mxnet,zhreshold/mxnet,fullfanta/mxnet,zhreshold/mxnet,jiajiechen/mxnet,yajiedesign/mxnet,TuSimple/mxnet,larroy/mxnet,ykim362/mxnet,ForkedReposBak/mxnet,indhub/mxnet,yuruofeifei/mxnet,indhub/mxnet,jamesliu/mxnet,tlby/mxnet,dmlc/mxnet,luoyetx/mxnet,indhub/mxnet,tlby/mxnet,jamesliu/mxnet,ForkedReposBak/mxnet,jamesliu/mxnet,TuSimple/mxnet,navrasio/mxnet,tornadomeet/mxnet,jennyzhang0215/incubator-mxnet,precedenceguo/mxnet,CodingCat/mxnet,sxjscience/mxnet,sxjscience/mxnet,weleen/mxnet,tlby/mxnet,larroy/mxnet,precedenceguo/mxnet,dmlc/mxnet,vikingMei/mxnet,reminisce/mxnet,ptrendx/mxnet,leezu/mxnet,LinkHS/incubator-mxnet,weleen/mxnet,eric-haibin-lin/mxnet,eric-haibin-lin/mxnet,CodingCat/mxnet,navrasio/mxnet,zhreshold/mxnet,LinkHS/incubator-mxnet,zhreshold/mxnet,jiajiechen/mxnet,jennyzhang0215/incubator-mxnet,Northrend/mxnet,yuruofeifei/mxnet,mbaijal/incubator-mxnet,tornadomeet/mxnet,navrasio/mxnet,reminisce/mxnet,ForkedReposBak/mxnet,fullfanta/mxnet,jiajiechen/mxnet,yuruofeifei/mxnet,fullfanta/mxnet,jamesliu/mxnet,TuSimple/mxnet,luoyetx/mxnet,ykim362/mxnet,mbaijal/incubator-mxnet,tlby/mxnet,reminisce/mxnet,jennyzhang0215/incubator-mxnet,reminisce/mxnet,LinkHS/incubator-mxnet,vikingMei/mxnet,luoyetx/mxnet,vikingMei/mxnet,zhreshold/mxnet,zhreshold/mxnet,jamesliu/mxnet,fullfanta/mxnet,ptrendx/mxnet,larroy/mxnet,reminisce/mxnet,yuruofeifei/mxnet,DickJC123/mxnet,mbaijal/incubator-mxnet,jamesliu/mxnet,dmlc/mxnet,rahul003/mxnet,luoyetx/mxnet,zhreshold/mxnet,CodingCat/mxnet,ptrendx/mxnet,larroy/mxnet,ykim362/mxnet,reminisce/mxnet,navrasio/mxnet,fullfanta/mxnet,indhub/mxnet,dmlc/mxnet,fullfanta/mxnet,yuruofeifei/mxnet,Northrend/mxnet,navrasio/mxnet,szha/mxnet,DickJC123/mxnet,DickJC123/mxnet,DickJC123/mxnet,precedenceguo/mxnet,navrasio/mxnet,vikingMei/mxnet,tornadomeet/mxnet,dmlc/mxnet,szha/mxnet,yajiedesign/mxnet,eric-haibin-lin/mxnet,leezu/mxnet,leezu/mxnet,jennyzhang0215/incubator-mxnet,CodingCat/mxnet,weleen/mxnet,tlby/mxnet,ForkedReposBak/mxnet,mbaijal/incubator-mxnet,LinkHS/incubator-mxnet,tlby/mxnet,jamesliu/mxnet,Northrend/mxnet,yajiedesign/mxnet,jiajiechen/mxnet,precedenceguo/mxnet,ptrendx/mxnet,jiajiechen/mxnet,LinkHS/incubator-mxnet,sxjscience/mxnet,TuSimple/mxnet,luoyetx/mxnet,eric-haibin-lin/mxnet,tornadomeet/mxnet,ptrendx/mxnet,apache/incubator-mxnet,luoyetx/mxnet,yajiedesign/mxnet,precedenceguo/mxnet,apache/incubator-mxnet,yajiedesign/mxnet,ForkedReposBak/mxnet,rahul003/mxnet,weleen/mxnet,ptrendx/mxnet,tlby/mxnet,szha/mxnet,ForkedReposBak/mxnet,larroy/mxnet,larroy/mxnet,ykim362/mxnet,szha/mxnet,eric-haibin-lin/mxnet,jiajiechen/mxnet,tlby/mxnet,rahul003/mxnet,apache/incubator-mxnet,eric-haibin-lin/mxnet,TuSimple/mxnet,LinkHS/incubator-mxnet,leezu/mxnet,yuruofeifei/mxnet,LinkHS/incubator-mxnet,leezu/mxnet,ForkedReposBak/mxnet,CodingCat/mxnet,szha/mxnet,indhub/mxnet