[FIX] delivery: create_price_rules won't create unnecessary rules anymore
[FIX] delivery: create_price_rules won't create unnecessary rules anymore

When updating a carrier that is not "fixed" or "base_on_rule", this
method was creating unnecessary delivery.price.rule at each write.
This patch fixes this issue.

Closes PR #17443

hip-odoo/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo,ygol/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,ygol/odoo,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo