doc: fix setter of `event.cancelBubble`
Setter of event.cancelBubble needs 1 argument(value). And event.cancelBubble() is working if value is true. But it's not described properly.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Setter of event.cancelBubble needs 1 argument(value). And event.cancelBubble() is working if value is true. But it's not described properly.