clean: delete obsolete unlinking of .hg/graftstate
The responsibility for clearing it is now in
`cmdutil.clearunfinished()`, so we shouldn't have to unlink it in
`hg.clean()`.
Differential Revision: https://phab.mercurial-scm.org/D7992
#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