correct documentation for enum.html (GH-358) (GH-367)

(cherry picked from commit 6265842)

Author: Mariatta

Doc/library/enum.rst

@@ -24,8 +24,8 @@ Module Contents
 ---------------
 
 This module defines four enumeration classes that can be used to define unique
-sets of names and values: :class:`Enum`, :class:`IntEnum`, and
-:class:`IntFlags`.  It also defines one decorator, :func:`unique`, and one
+sets of names and values: :class:`Enum`, :class:`IntEnum`, :class:`Flag`, and
+:class:`IntFlag`.  It also defines one decorator, :func:`unique`, and one
 helper, :class:`auto`.
 
 .. class:: Enum