[FIX] hr_holidays: error during migration

Without this patch Email notification of leaved doesnt have the
action buttons('approve','refuse')

related to rev https://github.com/odoo-dev/odoo/commit/46ccb7036fc478e613667777c3cd59b6406aff17

addons/hr_holidays/models/hr_holidays.py

@@ -526,7 +526,7 @@ class Holidays(models.Model):
         for recipient in recipients:
             if recipient.id in done_ids:
                 continue
-            if recipient.user_ids and group_hr_user in recipient.user_ids[0].groups_id.ids:
+            if recipient.user_ids and group_hr_user in recipient.user_ids[0].groups_id:
                 group_data['group_hr_user'] |= recipient
                 done_ids.add(recipient.id)
         return super(Holidays, self)._notification_group_recipients(message, recipients, done_ids, group_data)