[bugfix]: fix incomplete class documentation in AppServiceImpl (apache#3162)

Author: bigcyy

hertzbeat-manager/src/main/java/org/apache/hertzbeat/manager/service/impl/AppServiceImpl.java

@@ -75,7 +75,8 @@
 
 /**
  * Monitoring Type Management Implementation
- * temporarily stores the monitoring configuration and parameter configuration in memory and then stores it in the
+ * Temporarily stores the monitoring configuration and parameter configuration in memory,
+ * and then persists it to a storage system.
  */
 @Service
 @Order(value = Ordered.HIGHEST_PRECEDENCE)