UT: Use `self` instead of class name

monkey/tests/unit_tests/monkey_island/cc/event_queue/test_pypubsub_island_event_queue.py

@@ -59,8 +59,8 @@ def test_subscribe_publish__with_event_body(
         event = None
 
         def __call__(self, event):
-            MyCallable.call_count += 1
-            MyCallable.event = event
+            self.call_count += 1
+            self.event = event
 
     event = "my event!"
     my_callable = MyCallable()