copies: delete obsolete comment in _changesetforwardcopies()

IIRC, the comment applied to the filtering we did before 35d674a3d5db
(copies: don't filter out copy targets created on other side of merge
commit, 2019-04-18).

Differential Revision: https://phab.mercurial-scm.org/D6559

mercurial/copies.py

@@ -278,8 +278,6 b' def _changesetforwardcopies(a, b, match)'
             r, i2, copies2 = heapq.heappop(work)
             copies = {}
             allcopies = set(copies1) | set(copies2)
-            # TODO: perhaps this filtering should be done as long as ctx
-            # is merge, whether or not we're tracing from both parent.
             for dst in allcopies:
                 if not alwaysmatch and not match(dst):
                     continue