narrowchangegroup: remove backwards compatibility with old hg
This was missed in the initial import of narrowhg, but was detected by
the Python 3 porting effort once I got enough other things in narrow
fixed.
Differential Revision: https://phab.mercurial-scm.org/D2370
#require test-repo jshint hg10
$ . "$TESTDIR/helpers-testrepo.sh"
run jshint on all tracked files ending in .js except vendored dependencies
$ cd "`dirname "$TESTDIR"`"
$ testrepohg locate 'set:**.js' \
> 2>/dev/null \
> | xargs jshint