[FIX] delivery: cast to float
[FIX] delivery: cast to float

Some providers (e.g. Fedex) return a `decimal.Decimal` instead of a
`float`, which causes a crash.

opw-1903784

closes odoo/odoo#29311
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo