Remove old void cast

Author: brandtbucher

Python/gc.c

@@ -1320,7 +1320,7 @@ handle_resurrected_objects(PyGC_Head *unreachable, PyGC_Head* still_unreachable,
     // have the PREV_MARK_COLLECTING set, but the objects are going to be
     // removed so we can skip the expense of clearing the flag.
     PyGC_Head* resurrected = unreachable;
-    (void)deduce_unreachable(resurrected, still_unreachable);
+    deduce_unreachable(resurrected, still_unreachable);
     clear_unreachable_mask(still_unreachable);
 
     // Move the resurrected objects to the old generation for future collection.