bpo-39573: Use the Py_TYPE() macro (GH-21433)

Replace obj->ob_type with Py_TYPE(obj).
diff --git a/Tools/scripts/combinerefs.py b/Tools/scripts/combinerefs.py
index 49ccca7..848bae5 100755
--- a/Tools/scripts/combinerefs.py
+++ b/Tools/scripts/combinerefs.py
@@ -33,7 +33,7 @@
 
 if the refcount changed.
 
-typename is object->ob_type->tp_name, extracted from the second PYTHONDUMPREFS
+typename is Py_TYPE(object)->tp_name, extracted from the second PYTHONDUMPREFS
 output block.
 
 repr is repr(object), extracted from the first PYTHONDUMPREFS output block.