add note

client/src/main/java/org/apache/rocketmq/client/consumer/MQPushConsumer.java

@@ -55,6 +55,9 @@ public interface MQPushConsumer extends MQConsumer {
     void subscribe(final String topic, final String subExpression) throws MQClientException;
 
     /**
+     * This method will be removed in the version 5.0.0，because filterServer was removed,and method <code>subscribe(final String topic, final MessageSelector messageSelector)</code>
+     * is recommended.
+     * 
      * Subscribe some topic
      *
      * @param fullClassName full class name,must extend org.apache.rocketmq.common.filter. MessageFilter

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

@@ -720,6 +720,10 @@ public class MQClientInstance {
 
         return false;
     }
+    /**
+     * This method will be removed in the version 5.0.0，because filterServer was removed,and method <code>subscribe(final String topic, final MessageSelector messageSelector)</code>
+     * is recommended.
+     */
     @Deprecated
     private void uploadFilterClassToAllFilterServer(final String consumerGroup, final String fullClassName,
         final String topic,