[MINOR][DOCS] Document 'without' value for HADOOP_VERSION in pip installation
[MINOR][DOCS] Document 'without' value for HADOOP_VERSION in pip installation

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

I believe it's self-descriptive.

### Why are the changes needed?

To document supported features.

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

Yes, the docs are updated. It's master only.

### How was this patch tested?

Manually built the docs via `cd python/docs` and `make clean html`:

![Screen Shot 2020-11-20 at 10 59 07 AM](https://user-images.githubusercontent.com/6477701/99748225-7ad9b280-2b1f-11eb-86fd-165012b1bb7c.png)

Closes #30436 from HyukjinKwon/minor-doc-fix.

Authored-by: HyukjinKwon <2680965ad5aae29275c8fb10150cb10f5554e78b@apache.org>
Signed-off-by: HyukjinKwon <2680965ad5aae29275c8fb10150cb10f5554e78b@apache.org>

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