调整画板心跳返回数据

mec-websocket/src/main/java/com/ym/mec/web/handler/WhiteboardHandler.java

@@ -123,6 +123,7 @@ public class WhiteboardHandler {
                 .builder()
                 .event(EVENT_HEARTBEAT_SYNC)
                 .timestamp(DateTime.now().getMillis())
+                .interval(60)
                 .build();
 
         client.sendEvent(EVENT_HEARTBEAT_CONFIG, config);