Withdraw Calendar Event Message

Withdraws the event's held or approved message so the event can be changed: cancels the message and closes its approval round as withdrawn, recording who withdrew it. While a message is held or approved its settings and send time are locked; after withdrawing, edit the event and send it for approval again. Anyone who can edit the event can withdraw. Refused once the message is queued and within a minute of sending or past its send time. Returns the event message in the same shape as get_calendar_event_message.