Assigning PRs to merger doesn't work when they're auto-merged

[jsoref]

A bunch of [@jsoref's] PRs are assigned to the people who merged them. It feels like the automation hasn't contemplated that PRs would be written by people who can't/won't be the people who will click the "merge" button.

This is intentional: https://github.com/github/codeql-action/blob/bc64d12bb9f349435efba65d373bac054665b85f/.github/update-release-branch.py#L163-L168

More interesting is that this approach seems to break when enabling auto-merge as can be seen here: (merged by @angelapwen but PR is from @jsoref)

#2110 (@jsoref)

Originally posted by @intrigus-lgtm in https://github.com/github/codeql-action/issues/2131#issuecomment-1942529486