docs: update mqtt.md (midwayjs#4343)

* Update mqtt.md

* Update mqtt.md

Author: miraizhao

site/docs/extensions/mqtt.md

@@ -137,7 +137,7 @@ export default {
 import { ILogger, Inject } from '@midwayjs/core';
 import { Context, IMqttSubscriber, MqttSubscriber } from '@midwayjs/mqtt';
 
-@MqttSubscriber('test')
+@MqttSubscriber('sub1')
 export class Sub1Subscriber implements IMqttSubscriber {
 
   @Inject()

site/i18n/en/docusaurus-plugin-content-docs/current/extensions/mqtt.md

@@ -137,7 +137,7 @@ We can provide a standard subscriber implementation in a directory, such as `src
 import { ILogger, Inject } from '@midwayjs/core';
 import { Context, IMqttSubscriber, MqttSubscriber } from '@midwayjs/mqtt';
 
-@MqttSubscriber('test')
+@MqttSubscriber('sub1')
 export class Sub1Subscriber implements IMqttSubscriber {
 
    @Inject()