enhance: remove unused fetchRemoteConfigExecutorService in MQClientInstance

Author: Kris20030907

client/src/main/java/org/apache/rocketmq/client/impl/factory/MQClientInstance.java

@@ -134,12 +134,6 @@ public class MQClientInstance {
     private final Set<String/* Broker address */> brokerSupportV2HeartbeatSet = new HashSet<>();
     private final ConcurrentMap<String, Integer> brokerAddrHeartbeatFingerprintTable = new ConcurrentHashMap<>();
     private final ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(r -> new Thread(r, "MQClientFactoryScheduledThread"));
-    private final ScheduledExecutorService fetchRemoteConfigExecutorService = Executors.newSingleThreadScheduledExecutor(new ThreadFactory() {
-        @Override
-        public Thread newThread(Runnable r) {
-            return new Thread(r, "MQClientFactoryFetchRemoteConfigScheduledThread");
-        }
-    });
     private final PullMessageService pullMessageService;
     private final RebalanceService rebalanceService;
     private final DefaultMQProducer defaultMQProducer;