refactor: only use SET_SIZE, don't touch buffer metadata

Author: KowalskiThomas

Objects/listobject.c

@@ -3258,9 +3258,7 @@ _PyList_AsTupleAndClear(PyListObject *self)
     Py_BEGIN_CRITICAL_SECTION(self);
     PyObject **items = self->ob_item;
     Py_ssize_t size = Py_SIZE(self);
-    self->ob_item = NULL;
     Py_SET_SIZE(self, 0);
-    self->allocated = 0;
     ret = _PyTuple_FromArraySteal(items, size);
     free_list_items(items, false);
     Py_END_CRITICAL_SECTION();