Update KafkaCanalConnector.java (#4927)

update fastjson to fastjson2

client/src/main/java/com/alibaba/otter/canal/client/kafka/KafkaCanalConnector.java

@@ -1,6 +1,6 @@
 package com.alibaba.otter.canal.client.kafka;
 
-import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson2.JSON;
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;