[FIX] sale: have sender in SO confirmation email

Before 13.0 .sudo() before sending a mail would send it as superuser user
(which was the intention in this case), but since 13.0 for the same
intention we need .with_user(SUPERUSER_ID).

Without this change, the confirmation email on a sale order would have
no sender ending up in failure.

opw-2118612
closes #39737

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>