view .arcconfig @ 51737:48eb51494a7a

rustfmt: update expected Rust edition

In this case it doesn't change anything, but we've been using 2021 for a
while now.

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