fix 'directory' spell bug

dolphinscheduler-common/src/main/java/org/apache/dolphinscheduler/common/model/Server.java

@@ -40,7 +40,7 @@ public class Server {
     private int port;
 
     /**
-     * master direcotry in zookeeper
+     * master directory in zookeeper
      */
     private String zkDirectory;