docs(kitex): supplement deprecation details for connection multiplexing (#1530)

Author: ChocoLZS

content/en/docs/kitex/Tutorials/basic-feature/connection_type.md

@@ -84,7 +84,7 @@ The setting of parameters is suggested as follows:
 > **⚠️ Deprecated**
 >
 > - `WithMuxConnection` and `WithMuxTransport` rely on [`netpollmux`](https://github.com/cloudwego/kitex/pull/1933) which is no longer maintained
-> - The performance gain is not significant in actual business scenarios
+> - Connection multiplexing shows significant performance gains in stress testing scenarios, but in real business scenarios, the throughput is usually not high enough to benefit significantly; considering the maintenance costs, it has been deprecated and will no longer be maintained
 > - The server must enable this feature first, otherwise, it may lead to request failure if used improperly
 
 The client invokes the Server only need one connection normally when enabling Connection Multiplexing. Connection Multiplexing not only reduces the number of connections but also performs better than Connection Pool.

content/zh/docs/kitex/Tutorials/basic-feature/connection_type.md

@@ -85,7 +85,7 @@ xxxCli := xxxservice.NewClient("destServiceName", client.WithLongConnection(conn
 > **⚠️ 已废弃**
 >
 > - `WithMuxConnection` 和 `WithMuxTransport` 所依赖的 [`netpollmux`](https://github.com/cloudwego/kitex/pull/1933) 不再维护
-> - 在实际业务场景中性能收益不显著
+> - 连接多路复用在极限测试场景下性能收益显著，但在真实业务场景中，由于吞吐量通常不高，收益有限；综合考虑维护成本，决定废弃不再迭代
 > - 服务端需要先启用此功能，否则使用不当可能导致请求失败
 
 开启连接多路复用，Client 访问 Server 常规只需要**1个连接**即可，相比连接池极限测试吞吐表现更好（目前的极限测试配置了2个连接），且能大大减少连接数量。