It seems, you have to contact support and ask them to remove the commit in question. This FAQ was written before the introduction of Activity View. Pull requests always had the problem that force-pushes could not be deleted from the history shown in the PR. That's why I avoided them for my own repositories and simply merged the branches manually.
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[ 4.7 ms ] story [ 18.9 ms ] threadhttps://docs.github.com/en/authentication/keeping-your-accou...