### What changes were proposed in this pull request?
This PR revise the installation to describe `pip install pyspark[pandas_on_spark]` and removes pandas-on-Spark installation and videos/blogposts.
### Why are the changes needed?
pandas-on-Spark installation is merged to PySpark installation pages. For videos/blogposts, now this is named pandas API on Spark. Old Koalas blogposts and videos are obsolete.
### Does this PR introduce _any_ user-facing change?
To end users, no because the docs are not released yet.
### How was this patch tested?
I manually built the docs and checked the output
Closes#33018 from HyukjinKwon/SPARK-35645.
Authored-by: Hyukjin Kwon <gurwls223@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
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