bpo-39573: Finish converting to new Py_IS_TYPE() macro (GH-18601)

diff --git a/Objects/namespaceobject.c b/Objects/namespaceobject.c
index 5c7163f..a28b9e5 100644
--- a/Objects/namespaceobject.c
+++ b/Objects/namespaceobject.c
@@ -72,7 +72,7 @@
     PyObject *separator, *pairsrepr, *repr = NULL;
     const char * name;
 
-    name = (Py_TYPE(ns) == &_PyNamespace_Type) ? "namespace"
+    name = Py_IS_TYPE(ns, &_PyNamespace_Type) ? "namespace"
                                                : Py_TYPE(ns)->tp_name;
 
     i = Py_ReprEnter(ns);