gh-96641: Do not expose `KeyWrapper` in `_functoolsmodule.c` (gh-96642)

Misc/NEWS.d/next/Core and Builtins/2022-09-07-13-38-37.gh-issue-96641.wky0Fc.rst

+Do not expose ``KeyWrapper`` in :mod:`_functools`.

Modules/_functoolsmodule.c

@@ -1471,9 +1471,8 @@ _functools_exec(PyObject *module)
     if (state->keyobject_type == NULL) {
         return -1;
     }
-    if (PyModule_AddType(module, state->keyobject_type) < 0) {
-        return -1;
-    }
+    // keyobject_type is used only internally.
+    // So we don't expose it in module namespace.
 
     state->lru_list_elem_type = (PyTypeObject *)PyType_FromModuleAndSpec(
         module, &lru_list_elem_type_spec, NULL);