Step to reproduce:

- go to sale app
- select several SO
- action menu > delete
- got a traceback

Change the unlink definition to get multiple elements with mapped.
This fix an issue introduced on PR 72253

opw-2605699

closes odoo/odoo#73942

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>