clfilter: `bookmark.validdest` should run on unfiltered repo

The logic recently added to `bookmark.validdest` uses data about obsolete
changesets to see if a bookmark destination is valid. Obsolete changesets
are likely to be filtered, so we need to work on an unfiltered repository.

mercurial/bookmarks.py

@@ -256,6 +256,7 b' def diff(ui, dst, src):'
 
 def validdest(repo, old, new):
     """Is the new bookmark destination a valid update from the old one"""
+    repo = repo.unfiltered()
     if old == new:
         # Old == new -> nothing to update.
         return False