hidden: drop obsolete comment about cacheability

The cache was recently dropped, so I believe the comment is now obsolete.

mercurial/repoview.py

@@ -29,7 +29,7 b' def hideablerevs(repo):'
     return obsolete.getrevs(repo, 'obsolete')
 
 def revealedrevs(repo):
-    """non-cacheable revisions blocking hidden changesets from being filtered
+    """revisions blocking hidden changesets from being filtered
     """
 
     cl = repo.changelog