Fix example app cancel notification
Fix example app cancel notification

The `lastId` should reflect the last id used not the next id to be used.
When the lastId is set to the next id to be used the `cancelNotif`
function will try to cancel a id not yet used.

zo0r/react-native-push-notification,zo0r/react-native-push-notification,zo0r/react-native-push-notification