refactor: 移除未使用的GameFrameX.Proto.BuiltIn命名空间引用

Author: AlianBlank

GameFrameX.StartUp/DiscoverCenter/GameAppClient.cs

@@ -35,7 +35,6 @@
 using GameFrameX.NetWork;
 using GameFrameX.NetWork.Abstractions;
 using GameFrameX.NetWork.Messages;
-using GameFrameX.Proto.BuiltIn;
 using GameFrameX.SuperSocket.ClientEngine;
 using GameFrameX.Utility;