Fix a test

Author: srittau

stubs/python-dateutil/@tests/test_cases/check_inheritance.py

@@ -10,7 +10,7 @@ class MyDateTime(datetime):
 
 d = MyDateTime.now()
 x = d - relativedelta(days=1)
-assert_type(x, MyDateTime)
+assert_type(x, datetime[None])
 
 d3 = datetime.today()
 x3 = d3 - relativedelta(days=1)