Automerge does not block on successful tests, isn't useful

[jaraco]

In pascalgn/automerge-action#137, I reported an issue and learned that the automerge functionality only works on repositories that enable protected branches. This limitation makes the functionality no different than clicking 'merge'. That makes this functionality impractical to apply to repositories generally. Each repo that wishes to employ it needs to do so with knowledge about the constraints and repo-specific factors. Therefore, I propose to remove it.

[jaraco]

Also, Github now offers the feature natively.