We are currently using merge-bot for syncing release branches of our downstream forks with their upstream repos. `merge-bot` was forked a few years ago and the resulting tool, rebasebot, is significantly more advanced and we are the only team left using and maintaining merge-bot.

We should migrate our jobs to use rebasebot instead of merge-bot. This will require:

1. Identify and document the differences, if any, between rebasebot and mergebot.
2. Migrate a single repo to rebasebot, documenting the steps as a migration guide and ensuring we get successful migrations.
3. Migrate remaining repos.