largefiles: remove invalid comment (issue3065)

This comment is invalid.  The hg.update() function will abort in the case of
any genuine error, so there is nothing to check.  If we have gotten to this
point in execution, nothing critical has gone wrong, and if any standins
have been updated, we must pull new largefiles.

hgext/largefiles/overrides.py

@@ -591,7 +591,6 b' def override_revert(orig, ui, repo, *pat'
 
 def hg_update(orig, repo, node):
     result = orig(repo, node)
-    # XXX check if it worked first
     lfcommands.updatelfiles(repo.ui, repo)
     return result