Python 3.14 nightly failing

[AA-Turner]

Describe the bug

The test_singledispatchmethod_* tests in tests/test_extensions/test_ext_autodoc.py are newly failing on deadsnakes (Python 3.14)

• [TESTING] deadsnakes singledispatch failures #13360
• gh-127750: Fix and optimize functools.singledispatchmethod() python/cpython#130008

A