dirstate: remove now-unused .directories() method

It calls _rustmap.directories() which was already removed

Differential Revision: https://phab.mercurial-scm.org/D11458

mercurial/dirstate.py

@@ -344,9 +344,6 b' class dirstate(object):'
 
     iteritems = items
 
-    def directories(self):
-        return self._map.directories()
-
     def parents(self):
         return [self._validate(p) for p in self._pl]
 

mercurial/dirstatemap.py

@@ -700,9 +700,6 b' if rustmod is not None:'
         def copymap(self):
             return self._rustmap.copymap()
 
-        def directories(self):
-            return self._rustmap.directories()
-
         def debug_iter(self):
             return self._rustmap.debug_iter()