Feature flag clean up review_apps_redeploy_mr_widget

What does this MR do and why?

Moving !123207 (closed) into a new MR and continuing the work to clean up the FF review_apps_redeploy_mr_widget

Screenshots or screen recordings

How to set up and validate locally

1. Ensure flag is cleaned up
2. Ensure on an MR with a deploy job (environment) that everything works

I.E

environment: 
  name: production
  url: https://www.google.com/

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #407456 (closed)