[3.12] gh-119704: Fix reference leak in the ``Python/Python-tokenize.…

…c`` (GH-119705) (#119708)

Python/Python-tokenize.c

@@ -313,6 +313,7 @@ static void
 tokenizeriter_dealloc(tokenizeriterobject *it)
 {
     PyTypeObject *tp = Py_TYPE(it);
+    Py_XDECREF(it->last_line);
     _PyTokenizer_Free(it->tok);
     tp->tp_free(it);
     Py_DECREF(tp);