match: remove last traces of unused .missing callback

mercurial/match.py

@@ -132,9 +132,6 b' class match(object):'
     # by recursive traversal is visited.
     traversedir = None
 
-    def missing(self, f):
-        pass
-
     def rel(self, f):
         '''Convert repo path back to path that is relative to cwd of matcher.'''
         return util.pathto(self._root, self._cwd, f)