Revert "bpo-38659: [Enum] add _simple_enum decorator (GH-25285)" (GH-25476)

This reverts commit dbac8f40e81eb0a29dc833e6409a1abf47467da6.
diff --git a/Doc/library/enum.rst b/Doc/library/enum.rst
index 91c214e..bc88303 100644
--- a/Doc/library/enum.rst
+++ b/Doc/library/enum.rst
@@ -621,3 +621,4 @@
       Traceback (most recent call last):
       ...
       ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE
+