message: Update readme-facebook.md
  fix code sample
diff: @@ -610,7 +610,7 @@ Allows the Primary Receiver app to retrieve the list of apps that are Secondary
  - To retrieve the list of Secondary Receivers:
  ```javascript
  -controller.api.handover.get_secondary_receivers_list('id,name', function (result) {
  +controller.api.handover.get_secondary_receivers_list('id,name', function (err, result) {
  // result.data = list of Secondary Receivers
  });
  ```
  