.arcconfig

largefiles: explicitly set the source and sink types to 'hg' for lfconvert

I stumbled into this prior to adding the type indicator on the source and sink,
but there's no reason to try to infer the types for this conversion.

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