docs: fix ssizeobjargproc parameters (GH-100736)

(cherry picked from commit 5fb1c08)

Co-authored-by: David Lechner <[email protected]>

Author: miss-islington

Doc/c-api/typeobj.rst

@@ -450,6 +450,7 @@ slot typedefs
 |                             |                             |                      |
 |                             |    :c:type:`PyObject` *     |                      |
 |                             |    :c:type:`Py_ssize_t`     |                      |
+|                             |    :c:type:`PyObject` *     |                      |
 +-----------------------------+-----------------------------+----------------------+
 | :c:type:`objobjproc`        | .. line-block::             | int                  |
 |                             |                             |                      |
@@ -2589,7 +2590,7 @@ Slot Type typedefs
 
 .. c:type:: PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t)
 
-.. c:type:: int (*ssizeobjargproc)(PyObject *, Py_ssize_t)
+.. c:type:: int (*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *)
 
 .. c:type:: int (*objobjproc)(PyObject *, PyObject *)