Update test/asynchronous/test_server_selection_in_window.py

Co-authored-by: Noah Stapp <noah@noahstapp.com>

Author: sleepyStick

test/asynchronous/test_server_selection_in_window.py

@@ -121,7 +121,7 @@ def frequencies(self, client, listener, n_finds=10):
         for task in tasks:
             await task.start()
         for task in tasks:
-            task.join()
+            await task.join()
         for task in tasks:
             self.assertTrue(task.passed)