fix test websocket echo server

Author: psygames

Assets/UnityWebSocket/Demo/DemoScene.unity

@@ -164,7 +164,7 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: c1b55962346f6de40bd5e924df2854fb, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
-  address: wss://104.156.140.165:9003
+  address: wss://echo.websocket.events
   sendText: Hello World!
   logMessage: 1
 --- !u!1 &902376145