New compile warnings in `Py_SETREF`

[sobolevn]

After #99737 we got a bunch of new warnings:

Link: https://github.com/python/cpython/pull/99737/files#diff-7c8590641fc0d835bdab9395a95dbacfb2abb056cec4217466c0f3ca6cca8270R337

cc @vstinner

[vstinner]

Oops. I created #99781 to fix these warnings.

[vstinner]

Fixed by 5556d3e