.arcconfig

manifest: reject lines shorter than 42 bytes, not 22

Yuya correctly spotted during the review of f27f8e9ef1e73 that we're
dealing with hexlified hashes here, and so it should be 42 bytes not
22.

Differential Revision: https://phab.mercurial-scm.org/D5347

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