Admins cannot remove/change an event when its an invitation

[GretaD]

### Steps to reproduce 1. I accepted an invitation and move the event to a public calendar i didnt create 2. I asked the admins to delete or move that event to my personal cal as i dont have access 3. Admins cannot do anything but view this event ### Expected behaviour Admins can edit the event ### Actual behaviour Admins of that calendar cannot do anything to this event ### Calendar app **Calendar app version:** 3.0.4 on our cloud

[st3iny]

Related to https://github.com/nextcloud/calendar/issues/3866#issuecomment-1007968236.

[st3iny]

Admins can edit the event

We need to think about this. It could be fixed by https://github.com/nextcloud/calendar/issues/3883.