chore(test_mqtt): 修复端口号后多余空格并添加测试注释

调整了PORT变量行的末尾空格，新增了一行测试注释用于调试

test_mqtt.py

@@ -9,7 +9,7 @@ import signal
 import paho.mqtt.client as mqtt
 
 HOST = 'xt.wenhq.top'
-PORT = 8581
+PORT = 8581 
 TOPIC_PREFIX = '线架系统'
 
 received = {}
@@ -78,3 +78,4 @@ client.on_disconnect = on_disconnect
 print(f"正在连接 {HOST}:{PORT} ...")
 client.connect(HOST, PORT, keepalive=60)
 client.loop_forever()
+# test hook