bundlespec: phase out the `_bundlespeccgversions` mapping
The `_bundlespeccgversions` mapping is redundant with the `cg.version`
parameter. We move all users to the `cg.version` version and phase out the
`_bundlespeccgversions` mapping.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}