Fix new lint failure. (#7382)

F632 use ==/!= to compare str, bytes, and int literals.

Author: tseaver

tests/unit/test_page_iterator.py

@@ -514,7 +514,7 @@ def test_iterate_with_max_results(self):
 
         method.assert_called_with(request)
         assert method.call_count == 2
-        assert request.page_token is "1"
+        assert request.page_token == "1"
 
 
 class GAXPageIterator(object):