Remove tickets_attendee path from storage helpers

**Description**
`'ticket_attendee': 'attendees/tickets/pdf/{identifier}'`
can be safely removed from storage helpers as we've moved to `'tickets_all': generated/orders/tickets/pdf/...` so that co-organizers, organizers and attendees could download the tickets.

**Additional Context**
Just to be sure, please check if any of the downloads break by any chance because of this.