gh-95369: add missing decref in error case of exception group's split (GH-95370)

(cherry picked from commit bceb197)

Co-authored-by: Irit Katriel <[email protected]>

Author: miss-islington

Objects/exceptions.c

@@ -1114,6 +1114,7 @@ exceptiongroup_split_recursive(PyObject *exc,
             assert(PyList_CheckExact(match_list));
             if (PyList_Append(match_list, rec_result.match) < 0) {
                 Py_DECREF(rec_result.match);
+                Py_XDECREF(rec_result.rest);
                 goto done;
             }
             Py_DECREF(rec_result.match);