Fix checkstyle.

broker/src/main/java/org/apache/rocketmq/broker/subscription/SubscriptionGroupManager.java

@@ -16,7 +16,6 @@
  */
 package org.apache.rocketmq.broker.subscription;
 
-import java.io.File;
 import java.util.Iterator;
 import java.util.Map.Entry;
 import java.util.concurrent.ConcurrentHashMap;

broker/src/main/java/org/apache/rocketmq/broker/topic/TopicConfigManager.java

@@ -16,7 +16,6 @@
  */
 package org.apache.rocketmq.broker.topic;
 
-import java.io.File;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;