Group admins/mods should have the ability to unlink an event from the group
Currently, event-group connections can be created by any group member. This is usually fine, but there may be cases where a member connects an event to a group, but inappropriately. In these cases, group admins should have the ability to remove the connection.
Note that this should not require the ability to edit the event in other ways. Probably something as simple as a "Disconnect from group" button, visible to group admins.