[FIX] crm: used cr date for date_closed

This is mainly here to avoid future randomness on tests and have a
coherent value with previous commits

Part-of: odoo/odoo#85525

addons/event/models/event_registration.py

@@ -89,7 +89,7 @@ class EventRegistration(models.Model):
         for registration in self:
             if not registration.date_closed:
                 if registration.state == 'done':
-                    registration.date_closed = fields.Datetime.now()
+                    registration.date_closed = self.env.cr.now()
                 else:
                     registration.date_closed = False