Poll: stop changing `#` to `GH-` on PR merge

There is already an existing working solution: use automerge. I don’t use automerge for the reasons listed in my post RFE automerge enhancements

Also, I’m not sure what happens if I put an automerge label while the CI is running, and then the author push further changes. Does it remove the label? Or does it push the code that I didn’t review?