New warning: "‘_session_is_active’ defined but not used [-Wunused-function]"

# Bug report

<img width="536" alt="Снимок экрана 2023-11-03 в 11 51 48" src="https://github.com/python/cpython/assets/4660275/98a21700-9d5e-44b3-88f8-a7204bb3e6b6">

Introduced in https://github.com/python/cpython/commit/93206d19a35106f64a1aef5fa25eb18966970534
CC @ericsnowcurrently 


### Linked PRs
* gh-111706