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

* [Enum] revert enum module to 3.9
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 5db7a9b..a6549c7 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -1466,23 +1466,22 @@ class Float(float, enum.Enum):
             PI = 3.1415926
         class Int(enum.IntEnum):
             IDES = 15
-        class Str(enum.StrEnum):
-            # StrEnum uses the value and not the name for %s etc.
+        class Str(str, enum.Enum):
             ABC = 'abc'
         # Testing Unicode formatting strings...
         self.assertEqual("%s, %s" % (Str.ABC, Str.ABC),
-                         'abc, abc')
+                         'Str.ABC, Str.ABC')
         self.assertEqual("%s, %s, %d, %i, %u, %f, %5.2f" %
                         (Str.ABC, Str.ABC,
                          Int.IDES, Int.IDES, Int.IDES,
                          Float.PI, Float.PI),
-                         'abc, abc, 15, 15, 15, 3.141593,  3.14')
+                         'Str.ABC, Str.ABC, 15, 15, 15, 3.141593,  3.14')
 
         # formatting jobs delegated from the string implementation:
         self.assertEqual('...%(foo)s...' % {'foo':Str.ABC},
-                         '...abc...')
+                         '...Str.ABC...')
         self.assertEqual('...%(foo)s...' % {'foo':Int.IDES},
-                         '...IDES...')
+                         '...Int.IDES...')
         self.assertEqual('...%(foo)i...' % {'foo':Int.IDES},
                          '...15...')
         self.assertEqual('...%(foo)d...' % {'foo':Int.IDES},