changegroup: remove outdated comment

Differential Revision: https://phab.mercurial-scm.org/D4684

mercurial/changegroup.py

@@ -1120,9 +1120,6 b' class cgpacker(object):'
             commonctxs = [self._repo[c] for c in commonrevs]
             clrev = self._repo.changelog.rev
 
-            # Defining this function has a side-effect of overriding the
-            # function of the same name that was passed in as an argument.
-            # TODO have caller pass in appropriate function.
             def linknodes(flog, fname):
                 for c in commonctxs:
                     try: