[3.12] gh-107305: Update the C-API Docs for PEP 684 (gh-107324) (gh-107402)

gh-107305: Update the C-API Docs for PEP 684 (gh-107324)
(cherry picked from commit c0b81c4b5438a3565fadd9d6f5bc69f989a3fdee)

Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>