[3.12] gh-118310: Fix documentation for `enum.Enum.__new__` (GH-118311) (GH-118699)

gh-118310: Fix documentation for `enum.Enum.__new__` (GH-118311)

The provided example was incorrect:
- The example enum was missing the `int` mixin as implied by the context
- The value of `int('1a', 16)` was incorrectly given as 17
  (should be 26)
(cherry picked from commit 48e52fe2c9a7b33671f6b5d1420a71a6f31ad64b)

Co-authored-by: Momo Eissenhauer <mmEissen@users.noreply.github.com>