Fix worker failover service comment (#14494)

dolphinscheduler-master/src/main/java/org/apache/dolphinscheduler/server/master/service/WorkerFailoverService.java

@@ -208,13 +208,11 @@ public class WorkerFailoverService {
                                                   @Nullable ProcessInstance processInstance,
                                                   TaskInstance taskInstance) {
         if (processInstance == null) {
-            // This case should be happened.
             log.error(
                     "Failover task instance error, cannot find the related processInstance form memory, this case shouldn't happened");
             return false;
         }
         if (taskInstance == null) {
-            // This case should be happened.
             log.error("Master failover task instance error, taskInstance is null, this case shouldn't happened");
             return false;
         }