test-revlog-raw: drop the overwrite of dead code
The revlog class no longer have a _isgooddeltainfo method for a long time. So
overwriting it does not get us anything. The test have been wrapping the right
code since then anyway.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}