[3.10] gh-93738: Documentation C syntax (:c:type:`PyObject` -> :c:expr:`PyObject`) (GH-97776) (#97888)

:c:type:`PyObject` -> :c:expr:`PyObject`
(cherry picked from commit 0bf6a617ed1832bc4803e532c8d6b3427cf48b13)

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>