repoview: fix typo in repoview.changelog

Incidentally, this avoids the changelog cache being invalidated each time
it's accessed on a repoview.

On a filtering experiment on a repository the size of mozilla-central,
this makes a significant difference:

Before, running hg log -l 10 --time with about 8k changesets filtered out:
time: real 1.490 secs (user 1.450+0.000 sys 0.040+0.000)

After:
time: real 0.540 secs (user 0.530+0.000 sys 0.010+0.000)

mercurial/repoview.py

@@ -189,7 +189,7 b' class repoview(object):'
             # without change in the cachekey.
             oldfilter = cl.filteredrevs
             try:
-                cl.filterrevs = ()  # disable filtering for tip
+                cl.filteredrevs = ()  # disable filtering for tip
                 curkey = (len(cl), cl.tip(), hash(oldfilter))
             finally:
                 cl.filteredrevs = oldfilter