CLN: remove CategoricalIndex.unique (pandas-dev#40995)

Author: jbrockmendel

pandas/core/indexes/category.py

@@ -369,15 +369,6 @@ def fillna(self, value, downcast=None):
 
         return type(self)._simple_new(cat, name=self.name)
 
-    @doc(Index.unique)
-    def unique(self, level=None):
-        if level is not None:
-            self._validate_index_level(level)
-        result = self._values.unique()
-        # Use _simple_new instead of _shallow_copy to ensure we keep dtype
-        #  of result, not self.
-        return type(self)._simple_new(result, name=self.name)
-
     def reindex(
         self, target, method=None, level=None, limit=None, tolerance=None
     ) -> tuple[Index, np.ndarray | None]: