Check for undocumented C API failing (`PyException_HEAD`)

[tomasr8]

The check is failing on this seemingly unrelated 3.14 backport: https://github.com/python/cpython/actions/runs/29678674915/job/88170724647?pr=154011

cc @ZeroIntensity

Linked PRs

• [3.14] gh-154058: Fix failing C API docs check #154061

[ZeroIntensity]

Looks like I messed something up while handling some conflicts in ignored_c_api.txt. #143573 wasn't backported, so it doesn't run on docs PRs for 3.14 and 3.13.

cc @StanFromIreland, we should run the check on docs backports for 3.14 and 3.13

[StanFromIreland]

Backporting #143573 will be a little painful now, I might get to it at some point next week, if no one gets to it before then.