[3.14] gh-132246: Add special buffer methods to C API Type Object docs (gh-132247) (gh-134426)

Two special methods, __buffer__ and __release_buffer__ were added to
Python 3.12 by PEP 688. The C API Type Object documentation for slots
includes `tp_as_buffer`, and sub-slots `bf_getbuffer`, `bf_releasebuffer`
but does not refer to the Python Data Model version of those. Add the
missing references.

(cherry picked from commit b529b60fc239d19245e5fafd0514d90097c2eb40)

Co-authored-by: Cody Maloney <cmaloney@users.noreply.github.com>