[3.12] gh-116296: Fix refleak in reduce_newobj() corner case (GH-116297) (#116299)

(cherry picked from commit 17c4849981)

Co-authored-by: Erlend E. Aasland <erlend@python.org>
Co-authored-by: Brandt Bucher <brandtbucher@microsoft.com>

Objects/typeobject.c

@@ -6258,6 +6258,7 @@ reduce_newobj(PyObject *obj)
     }
     else {
         /* args == NULL */
+        Py_DECREF(copyreg);
         Py_DECREF(kwargs);
         PyErr_BadInternalCall();
         return NULL;