Introduce FF for skipping committer check for web commits
What does this MR do and why?
With Prepare push rules for committer email change (!146335 - merged), skipping commit checks for web commits where introduced with an assumption that author emails are always equal to committer emails.
However, users may specify commit emails:
The change should have been introduced behind a feature flag to enable the change more carefully. Let's fix it in this MR.