Gitlab::Git::Repository::GitError and Gitlab::Git::CommandError
errors can get raised when trying to cleanup MR refs. This will
result to the worker being retried and move to dead queue when
failed after the retry limit.

We don't need to retry in this case as the job will be scheduled
again when picked up by `ScheduleMergeRequestCleanupRefsWorker`
that runs every minute via sidekiq cron.