Replace Py_NotImplemented returns with the macro form Py_RETURN_NOTIMPLEMENTED.
The macro was introduced in #12724.
diff --git a/Modules/xxlimited.c b/Modules/xxlimited.c
index ec924f2..661b6e2 100644
--- a/Modules/xxlimited.c
+++ b/Modules/xxlimited.c
@@ -187,8 +187,7 @@
 static PyObject *
 null_richcompare(PyObject *self, PyObject *other, int op)
 {
-    Py_INCREF(Py_NotImplemented);
-    return Py_NotImplemented;
+    Py_RETURN_NOTIMPLEMENTED;
 }
 
 static PyType_Slot Null_Type_slots[] = {