[3.10] bpo-44559: [Enum] revert enum module to 3.9 (GH-27010)

* [Enum] revert enum module to 3.9
diff --git a/Lib/ast.py b/Lib/ast.py
index 66bcee8..f4d2f6e 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -27,7 +27,7 @@
 import sys
 from _ast import *
 from contextlib import contextmanager, nullcontext
-from enum import IntEnum, auto, _simple_enum
+from enum import IntEnum, auto
 
 
 def parse(source, filename='<unknown>', mode='exec', *,
@@ -636,8 +636,7 @@ class Param(expr_context):
 # We unparse those infinities to INFSTR.
 _INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)
 
-@_simple_enum(IntEnum)
-class _Precedence:
+class _Precedence(IntEnum):
     """Precedence table that originated from python grammar."""
 
     TUPLE = auto()