[ISSUE #10110] Plain request process success and response fail when tlsMode=enforcing (#10111)

Author: yuz10

remoting/src/main/java/org/apache/rocketmq/remoting/netty/NettyRemotingServer.java

@@ -525,6 +525,7 @@ protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) {
             } else if (tlsMode == TlsMode.ENFORCING) {
                 ctx.close();
                 log.warn("Clients intend to establish an insecure connection while this server is running in SSL enforcing mode");
+                throw new UnsupportedOperationException("The NettyRemotingServer in SSL enforcing mode doesn't support plain client");
             }
 
             try {