Follow-up from "Add Default Initial Branch Name for Repositories Group Setting"

The following discussion from !43290 (merged) should be addressed:

• @mwoolf started a discussion: (+4 comments)

  I'm not totally convinced by this method of specifying a redirect. 🤔 GroupsController#update is a very heavily utilized controller action and this change is expanding it quite a lot and adding a nested conditional statement.

  I wonder if this logic belongs in a separate controller entirely, similar to the deploy tokens settings on the same page? Or at the least, a different action within this controller? WDYT?

  As an example, updating CI/CD settings posts to Groups::Settings::CiCdController#update_auto_devops via /groups/GROUP_NAME/-/settings/ci_cd/update_auto_devops rather than the groups controller