Check the auto merge worker when project setting regex updated

What does this MR do and why?

We need to recheck the auto merge of the project merge requests when the regex is updated.

To Test:

• Turn on feature flag (merge_request_title_regex)
• Require a regex in the project setting
• Have an MR that doesn't match it but otherwise mergable
• Set auto merge for that MR
• Remove the regex
• See it is merged

Related to #537161 (closed)