修改Mqtt的bug

seatunnel-datasource/seatunnel-datasource-plugins/datasource-mqtt/src/main/java/org/apache/seatunnel/datasource/plugin/mqtt/InitCallback.java

@@ -18,7 +18,7 @@ import java.util.List;
 @Slf4j
 public class InitCallback implements MqttCallback {
 
-    private List<MqttMessage> mqttMessageList=new ArrayList<>();
+    private List<MqttMessage> mqttMessageList = new ArrayList<>();
 
     public List<MqttMessage> getMqttMessageList() {
         return mqttMessageList;