[SPARK-40006][PYTHON][DOCS][FOLLOW-UP] Remove unused Spark context and duplicated Spark session initialization
[SPARK-40006][PYTHON][DOCS][FOLLOW-UP] Remove unused Spark context and duplicated Spark session initialization

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

This PR is a followup of https://github.com/apache/spark/pull/37437 which missed to remove unused `sc` and duplicated Spark session initialization.

### Why are the changes needed?

To make the consistent example, and remove unused variables.

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

No. It's a documentation change. However, the previous PR is not released yet.

### How was this patch tested?

Ci in this PR should test it out.

Closes #37457 from HyukjinKwon/SPARK-40006-followup.

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

ueshin/apache-spark,HyukjinKwon/spark,vinodkc/spark,wangyum/spark,zero323/spark,hvanhovell/spark,zero323/spark,mahak/spark,zzcclp/spark,holdenk/spark,zero323/spark,dongjoon-hyun/spark,holdenk/spark,vinodkc/spark,mahak/spark,wangyum/spark,gengliangwang/spark,WeichenXu123/spark,WeichenXu123/spark,hvanhovell/spark,zzcclp/spark,mahak/spark,apache/spark,mahak/spark,wangyum/spark,shaneknapp/spark,WeichenXu123/spark,witgo/spark,WeichenXu123/spark,WeichenXu123/spark,zzcclp/spark,wangyum/spark,WeichenXu123/spark,srowen/spark,srowen/spark,wangyum/spark,vinodkc/spark,zzcclp/spark,gengliangwang/spark,wangyum/spark,apache/spark,hvanhovell/spark,witgo/spark,ueshin/apache-spark,shaneknapp/spark,apache/spark,shaneknapp/spark,dongjoon-hyun/spark,dongjoon-hyun/spark,zero323/spark,ueshin/apache-spark,witgo/spark,HyukjinKwon/spark,witgo/spark,shaneknapp/spark,apache/spark,holdenk/spark,zero323/spark,mahak/spark,vinodkc/spark,zero323/spark,ueshin/apache-spark,apache/spark,zzcclp/spark,dongjoon-hyun/spark,HyukjinKwon/spark,apache/spark,zero323/spark,srowen/spark,gengliangwang/spark,wangyum/spark,witgo/spark,ueshin/apache-spark,gengliangwang/spark,holdenk/spark,witgo/spark,apache/spark,zzcclp/spark,hvanhovell/spark,shaneknapp/spark,dongjoon-hyun/spark,gengliangwang/spark,srowen/spark,mahak/spark,HyukjinKwon/spark,holdenk/spark,holdenk/spark,hvanhovell/spark,hvanhovell/spark,HyukjinKwon/spark,zzcclp/spark,srowen/spark,holdenk/spark,shaneknapp/spark,dongjoon-hyun/spark,HyukjinKwon/spark,srowen/spark,srowen/spark,mahak/spark,ueshin/apache-spark,witgo/spark,vinodkc/spark,vinodkc/spark,hvanhovell/spark,shaneknapp/spark,HyukjinKwon/spark,gengliangwang/spark,ueshin/apache-spark,vinodkc/spark,gengliangwang/spark,dongjoon-hyun/spark,WeichenXu123/spark