Move auditing of approval rules to after merge

What does this MR do and why?

This auditing was originally in the approval rule class, and each time a approval rule was updated, it would be logged.

This is tricky for us to validate whether a code owner rule is valid or not, and after some discussion here #375060 (comment 1125662169) it was decided we can move the check to post merge.

To Test:

• Turn on setting to disallow authors to approve
• Create a merge request with you as the author, with an approval rule being just you
• Merge the merge request
• Check the audit logs for the project