Go through the usages of Repository#after_create_branch and correct if nescessary

I see that the GitGarbageCollectWorker is currently calling Repository#after_create_branch, while it should be calling expire_branches_cache, which would incorrectly track a repository_event.

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The following discussion from gitlab-ce!31653 should be addressed:

• @patrickbajao started a discussion: (+2 comments)

  Needed to add this flag for both after_create_branch and after_remove_branch as they're also being used outside the context of PostReceive. I'm not sure if removing calls for expire_branches_cache will break the behavior of those so I decided to have it conditional and can be disabled by the consumer (which can be seen in Git::BranchHooksService).