Use cached MessageSweeper field in RqueueUtilityServiceImpl.makeEmpty

The constructor already resolves MessageSweeper.getInstance(...) into
the messageSweeper field; makeEmpty was still calling the static
getInstance on every invocation. Just call the cached instance.

Pure cleanup — getInstance is a synchronized double-checked-lock
singleton that returns the same instance the field already holds, so
behaviour is unchanged. This lines makeEmpty up with how the rest of
the class uses its injected dependencies.

Assisted-By: Claude Code

Author: sonus21

rqueue-redis/src/main/java/com/github/sonus21/rqueue/redis/web/RqueueUtilityServiceImpl.java

@@ -223,13 +223,11 @@ public BooleanResponse makeEmpty(String queueName, String dataName) {
     if (type == null || type == org.springframework.data.redis.connection.DataType.NONE) {
       return new BooleanResponse(true);
     }
-    return new BooleanResponse(
-        MessageSweeper.getInstance(rqueueConfig, rqueueMessageTemplate, messageMetadataService)
-            .deleteAllMessages(MessageDeleteRequest.builder()
-                .dataName(dataName)
-                .queueName(queueName)
-                .dataType(type)
-                .build()));
+    return new BooleanResponse(messageSweeper.deleteAllMessages(MessageDeleteRequest.builder()
+        .dataName(dataName)
+        .queueName(queueName)
+        .dataType(type)
+        .build()));
   }
 
   private boolean shouldFetchVersionDetail() {