Remove old comment in Resolver.
`requirement_set` is no longer passed to
`Resolver._check_skip_installed`, so we do not need to mention it.
@@ -227,7 +227,6 @@ class Resolver(object):
req.conflicts_with = req.satisfied_by
req.satisfied_by = None
- # XXX: Stop passing requirement_set for options
def _check_skip_installed(self, req_to_install):
# type: (InstallRequirement) -> Optional[str]
"""Check if req_to_install should be skipped.
