gh-90716: Fix pylong_int_from_string() refleak (#99094)

Fix validated by:

    $ ./python -m test -R 3:3 test_int
    Tests result: SUCCESS

Author: vstinner

Objects/longobject.c

@@ -2376,6 +2376,7 @@ pylong_int_from_string(const char *start, const char *end, PyLongObject **res)
         goto error;
     }
     if (!PyLong_Check(result)) {
+        Py_DECREF(result);
         PyErr_SetString(PyExc_TypeError,
                         "_pylong.int_from_string did not return an int");
         goto error;