[FIX] event_sale: remove 'need to be paid' banner for free ticket

This commit fixes an issue where if a ticket is free, the registration would
still "need to be paid" by the attendee.

This behavior is contradictory for a free ticket, so the attendee now has to
pay the ticket if it is not paid and is not a free ticket.

task-3012928

closes odoo/odoo#102996

Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>

addons/event_sale/models/event_registration.py

@@ -128,6 +128,6 @@ class EventRegistration(models.Model):
         res.update({
             'payment_status': self.payment_status,
             'payment_status_value': dict(self._fields['payment_status']._description_selection(self.env))[self.payment_status],
-            'has_to_pay': not self.is_paid,
+            'has_to_pay': self.payment_status == 'to_pay',
         })
         return res