[FIX] event: remove duplicated method

Oversight of previous forward-port

addons/event/models/event.py

@@ -483,17 +483,6 @@ class EventRegistration(models.Model):
                 ]).write({'partner_id': new_partner.id})
         return super(EventRegistration, self)._message_post_after_hook(message, values, notif_layout)
 
-    @api.multi
-    def message_get_default_recipients(self):
-        # Prioritize registration email over partner_id, which may be shared when a single
-        # partner booked multiple seats
-        return {
-            r.id: {'partner_ids': [],
-                   'email_to': r.email,
-                   'email_cc': False}
-            for r in self
-        }
-
     @api.multi
     def action_send_badge_email(self):
         """ Open a window to compose an email, with the template - 'event_badge'