fix error type in ReservationCanceledEventHandler

[hhko]

Ex.

Before

var removeBookingResult = participant.RemoveFromSchedule(notification.Session);
if (removeBookingResult.IsError)
{
    throw new EventualConsistencyException(
        ReservationCanceledEvent.ParticipantNotFound

After

var removeBookingResult = participant.RemoveFromSchedule(notification.Session);
if (removeBookingResult.IsError)
{
    throw new EventualConsistencyException(
        ReservationCanceledEvent.ParticipantScheduleUpdateFailed           // <-