[FIX] sale_management: fix field's attribute
[FIX] sale_management: fix field's attribute

on_delete had no effect

closes odoo/odoo#32596

Signed-off-by: Martin Trigaux (mat) <cc7c5be316e48d137cbb549833b85d91034d799d@odoo.com>
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo