[FIX] sale_timesheet : fix the default value for timesheet_product_id
[FIX] sale_timesheet : fix the default value for timesheet_product_id

The timesheet_product_id is required if allow_billable is True and
it should have a default value.

Task-2199650

closes odoo/odoo#48028

Signed-off-by: Yannick Tivisse (yti) <200a91eb0e5cc4726d6a3430713b580138f34298@odoo.com>

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo