Remove unused approval auto merge worker

What does this MR do and why?

Originally we were only processing approvals, so we had a approval specific worker.

Now it is more general, we introduced a general worker (!145460 (merged)) and then switched over to using this instead (!145462 (merged))

This worker is not used any more (https://log.gprd.gitlab.net/app/r/s/kYT56) and can be removed