Cleanup concurrent column rename Pre-receive secret detection to Secret push protection

The following discussion from !177824 (merged) should be addressed:

• @serenafang started a discussion: (+9 comments)

  @a_akgun optionally the 3rd stem of rename_column_concurrently can be done in the current release, but pls open an issue if you want to do the cleanup later. https://docs.gitlab.com/ee/development/database/avoiding_downtime_in_migrations.html#renaming-columns

I've set this issue to %18.0, since that's when we'll be able to fully remove all references to pre_receive_secret_detection_enabled when we deprecate the API endpoints. Deprecate pre_receive_secret_detection_enabled ... (#514414 - closed), Deprecate pre_receive_secret_detection_enabled ... (#514413 - closed)