Use base _values for CategoricalIndex

Author: TomAugspurger

pandas/core/indexes/category.py

@@ -304,10 +304,6 @@ def values(self):
         """ return the underlying data, which is a Categorical """
         return self._data
 
-    @property
-    def _values(self):
-        return self._data
-
     @property
     def _ndarray_values(self):
         return self._data.codes