[FIX] mass_mailing_event_track: Correctly set recipients on mail wizard

Since odoo@f93c4f4 the
feature is not setting the recipients correctly when trying to send a mass mailing
to all the event tracks speakers.

addons/mass_mailing_event_track/models/event.py

@@ -16,7 +16,7 @@ def action_mass_mailing_track_speakers(self):
             view_mode='form',
             target='current',
             context=dict(
-                default_mailing_model=self.env.ref('website_event_track.model_event_track').id,
+                default_mailing_model_id=self.env.ref('website_event_track.model_event_track').id,
                 default_mailing_domain="[('event_id', 'in', %s), ('stage_id.is_cancel', '!=', True)]" % self.ids,
             ),
         )