SF bug 590366: Small typo in listsort:ParseTuple

The PyArg_ParseTuple() error string still said "msort".  Changed to "sort".

Objects/listobject.c

@@ -1619,7 +1619,7 @@ listsort(PyListObject *self, PyObject *args)
 
 	assert(self != NULL);
 	if (args != NULL) {
-		if (!PyArg_ParseTuple(args, "|O:msort", &compare))
+		if (!PyArg_ParseTuple(args, "|O:sort", &compare))
 			return NULL;
 	}
 	merge_init(&ms, compare);