[CAL-3696] disable default confirmation emails for attendees cannot be undone and breaks page

[Peer Richelsen]

test it here: cal.com/ghldirect

_{From SyncLinear.com | CAL-3696}

[GaryGHL]

To add, the form works fine on creation until the option above is selected. This then causes the error on submission, sometimes the booking is made, sometimes not. The redirect or confirmation page never shows. Unchecking the option doesn't resolve, only fix is to delete the event type and recreate without checking the attended email box, if you do, the error returns.