Update pydocs front page

A friend pointed out to me that the front page of pydocs doesn't do much to explain how to use Beam.
This is the page https://beam.apache.org/releases/pydoc/2.11.0/
It describes very little about how to write pipelines. Perhaps it'd be better to remove the Overview and Typical Usage sections and point people to the main documentation page (https://beam.apache.org/documentation/) instead?

Imported from Jira [BEAM-7089](https://issues.apache.org/jira/browse/BEAM-7089). Original Jira may contain additional context.
Reported by: udim.