[SPARK-32525][DOCS] The layout of monitoring.html is broken
[SPARK-32525][DOCS] The layout of monitoring.html is broken

### What changes were proposed in this pull request?

This PR fixes the layout of monitoring.html broken after SPARK-31566(#28354).
The cause is there are 2 `<td>` tags not closed in `monitoring.md`.

### Why are the changes needed?

This is a bug.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Build docs and the following screenshots are before/after.

* Before fixed
![broken-doc](https://user-images.githubusercontent.com/4736016/89257873-fba09b80-d661-11ea-90da-06cbc0783011.png)

* After fixed.
![fixed-doc2](https://user-images.githubusercontent.com/4736016/89257910-0fe49880-d662-11ea-9a85-7a1ecb1d38d6.png)

Of course, the table is still rendered correctly.
![fixed-doc1](https://user-images.githubusercontent.com/4736016/89257948-225ed200-d662-11ea-80fd-d9254b44d4a0.png)

Closes #29345 from sarutak/fix-monitoring.md.

Authored-by: Kousuke Saruta <7d45abe39fd242ee2f6575da28f13d66568418b3@oss.nttdata.com>
Signed-off-by: Gengliang Wang <bfe1a7b36425bd89859a70a36586361d28ec35eb@databricks.com>

mahak/spark,nchammas/spark,taroplus/spark,JoshRosen/spark,vinodkc/spark,jiangxb1987/spark,ueshin/apache-spark,shuangshuangwang/spark,chuckchen/spark,wzhfy/spark,rednaxelafx/apache-spark,srowen/spark,holdenk/spark,zzcclp/spark,holdenk/spark,cloud-fan/spark,chuckchen/spark,shuangshuangwang/spark,taroplus/spark,jiangxb1987/spark,gengliangwang/spark,maropu/spark,BryanCutler/spark,vinodkc/spark,cloud-fan/spark,HyukjinKwon/spark,vinodkc/spark,WeichenXu123/spark,mahak/spark,maropu/spark,holdenk/spark,xuanyuanking/spark,apache/spark,hvanhovell/spark,ueshin/apache-spark,chuckchen/spark,taroplus/spark,milliman/spark,milliman/spark,shuangshuangwang/spark,vinodkc/spark,vinodkc/spark,ueshin/apache-spark,dongjoon-hyun/spark,ptkool/spark,zero323/spark,witgo/spark,hvanhovell/spark,HyukjinKwon/spark,maropu/spark,vinodkc/spark,BryanCutler/spark,gengliangwang/spark,hvanhovell/spark,chuckchen/spark,shaneknapp/spark,BryanCutler/spark,holdenk/spark,taroplus/spark,srowen/spark,xuanyuanking/spark,WeichenXu123/spark,shaneknapp/spark,holdenk/spark,mahak/spark,hvanhovell/spark,BryanCutler/spark,maropu/spark,dongjoon-hyun/spark,HyukjinKwon/spark,wzhfy/spark,JoshRosen/spark,rednaxelafx/apache-spark,xuanyuanking/spark,nchammas/spark,mahak/spark,cloud-fan/spark,xuanyuanking/spark,wangmiao1981/spark,rednaxelafx/apache-spark,holdenk/spark,JoshRosen/spark,nchammas/spark,taroplus/spark,ueshin/apache-spark,wangmiao1981/spark,wzhfy/spark,milliman/spark,jiangxb1987/spark,ptkool/spark,shaneknapp/spark,apache/spark,zzcclp/spark,rednaxelafx/apache-spark,jiangxb1987/spark,xuanyuanking/spark,mahak/spark,ueshin/apache-spark,hvanhovell/spark,ptkool/spark,apache/spark,zero323/spark,nchammas/spark,ueshin/apache-spark,shuangshuangwang/spark,rednaxelafx/apache-spark,wangyum/spark,JoshRosen/spark,taroplus/spark,cloud-fan/spark,jiangxb1987/spark,cloud-fan/spark,BryanCutler/spark,ueshin/apache-spark,shuangshuangwang/spark,rednaxelafx/apache-spark,apache/spark,apache/spark,nchammas/spark,witgo/spark,ptkool/spark,JoshRosen/spark,HyukjinKwon/spark,witgo/spark,zero323/spark,gengliangwang/spark,vinodkc/spark,mahak/spark,witgo/spark,ptkool/spark,milliman/spark,wangyum/spark,shaneknapp/spark,milliman/spark,gengliangwang/spark,WeichenXu123/spark,nchammas/spark,maropu/spark,dongjoon-hyun/spark,hvanhovell/spark,taroplus/spark,wangmiao1981/spark,gengliangwang/spark,JoshRosen/spark,dongjoon-hyun/spark,chuckchen/spark,chuckchen/spark,WeichenXu123/spark,dongjoon-hyun/spark,zero323/spark,nchammas/spark,holdenk/spark,wzhfy/spark,witgo/spark,wangmiao1981/spark,ptkool/spark,gengliangwang/spark,zzcclp/spark,zero323/spark,wangyum/spark,zzcclp/spark,srowen/spark,wangyum/spark,xuanyuanking/spark,WeichenXu123/spark,dongjoon-hyun/spark,witgo/spark,HyukjinKwon/spark,hvanhovell/spark,wangyum/spark,shuangshuangwang/spark,wangyum/spark,xuanyuanking/spark,zzcclp/spark,srowen/spark,zero323/spark,wangmiao1981/spark,dongjoon-hyun/spark,witgo/spark,srowen/spark,BryanCutler/spark,rednaxelafx/apache-spark,milliman/spark,gengliangwang/spark,zero323/spark,mahak/spark,HyukjinKwon/spark,wangmiao1981/spark,wzhfy/spark,jiangxb1987/spark,zzcclp/spark,shuangshuangwang/spark,maropu/spark,cloud-fan/spark,wangyum/spark,wzhfy/spark,chuckchen/spark,ptkool/spark,shaneknapp/spark,shaneknapp/spark,zzcclp/spark,apache/spark,wangmiao1981/spark,cloud-fan/spark,HyukjinKwon/spark,jiangxb1987/spark,WeichenXu123/spark,milliman/spark,srowen/spark,apache/spark,WeichenXu123/spark,maropu/spark,srowen/spark,shaneknapp/spark,JoshRosen/spark,wzhfy/spark,BryanCutler/spark