Fix a false positive with ``singledispatchmethod-function`` (#9599) (#9605)

* Fix a false positive with ``singledispatchmethod-function`` when a method is decorated with both ``functools.singledispatchmethod`` and ``staticmethod``.

Closes #9531

(cherry picked from commit 6df4e1d238cec9151fd687a060bb74a1ea681e33)

Co-authored-by: Mark Byrne <31762852+mbyrnepr2@users.noreply.github.com>
16 files changed