Accept new Plex websocket callback payloads (#40773)

tests/components/plex/helpers.py

@@ -1,7 +1,8 @@
 """Helper methods for Plex tests."""
+from plexwebsocket import SIGNAL_DATA
 
 
 def trigger_plex_update(mock_websocket):
     """Call the websocket callback method."""
     callback = mock_websocket.call_args[0][1]
-    callback()
+    callback(SIGNAL_DATA, None, None)