tests: don't run test-update-atomic.t on chg
I am unable to find a good way to make `showwrites` extension in it to work with
chg. Also putting the use of showwrites inside `if no-chg` will defeat the
purpose of test, so I just made the test no-op on chg.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}