missing decref in error case of ExceptionGroup split()

[iritkatriel]

Noticed in the code:

            if (PyList_Append(match_list, rec_result.match) < 0) {
                Py_DECREF(rec_result.match);
                goto done;
            }

We are missing a Py_XDECREF(rec_result.rest); before the goto done.