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

This reverts commit dbac8f40e81eb0a29dc833e6409a1abf47467da6.
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 0e6cbb6..d47cf28 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -1463,21 +1463,20 @@ 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')
+                         'ABC, 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')
+                         'ABC, ABC, 15, 15, 15, 3.141593,  3.14')
 
         # formatting jobs delegated from the string implementation:
         self.assertEqual('...%(foo)s...' % {'foo':Str.ABC},
-                         '...abc...')
+                         '...ABC...')
         self.assertEqual('...%(foo)s...' % {'foo':Int.IDES},
                          '...IDES...')
         self.assertEqual('...%(foo)i...' % {'foo':Int.IDES},