[3.12] Docs: Fix documentation for "PyTypeObject Definition" (GH-130936) (GH-131459)

The structure definition for `PyTypeObject` is in `Include/cpython/object.h`,
not in `Include/object.h`.
(cherry picked from commit a0478c9f0c6d6a75ca35a8dc2c74d3b58877f094)

Co-authored-by: Yuki Kobayashi <drsuaimqjgar@gmail.com>