perf: fix perfcca to work with new casecollisionauditor interface

A recent changeset, afd75476939e, modified the caescollisionauditor interface
but did not update perf.py.  This changeset remidies that.

contrib/perf.py

@@ -177,7 +177,7 b' def perftemplating(ui, repo):'
     ui.popbuffer()
 
 def perfcca(ui, repo):
-    timer(lambda: scmutil.casecollisionauditor(ui, False, repo[None]))
+    timer(lambda: scmutil.casecollisionauditor(ui, False, repo.dirstate))
 
 def perffncacheload(ui, repo):
     from mercurial import scmutil, store