[FIX] project: count tasks of child contacts
[FIX] project: count tasks of child contacts

Allow to have the count to match the one you will get when clicking on
statbutton (behavior changed by #27118).

closes odoo/odoo#31081
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo