Consolidate python examples in enum documentaiton

The IntEnum example in the rst docs is the only example in which a
plural classname (Numbers) is used. This change fixes it by renaming
Numbers to Number.

Closes python#104659

Doc/library/enum.rst

@@ -406,18 +406,18 @@ Data Types
    with an *IntEnum* member, the resulting value loses its enumeration status.
 
       >>> from enum import IntEnum
-      >>> class Numbers(IntEnum):
+      >>> class Number(IntEnum):
       ...     ONE = 1
       ...     TWO = 2
       ...     THREE = 3
       ...
-      >>> Numbers.THREE
-      <Numbers.THREE: 3>
-      >>> Numbers.ONE + Numbers.TWO
+      >>> Number.THREE
+      <Number.THREE: 3>
+      >>> Number.ONE + Number.TWO
       3
-      >>> Numbers.THREE + 5
+      >>> Number.THREE + 5
       8
-      >>> Numbers.THREE == 3
+      >>> Number.THREE == 3
       True
 
    .. note::