repoview: fix changelog.__contains__ method
This have been around for ten years, so we can safely that this method have few
callers. However I am about to add one.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}