.arcconfig

repair: move ui.history-editing-backup to [rewrite] section

Since we have the "rewrite" section for general history-editing options, the
backup option should be there.

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}