[FIX] product: lock uom in edition
[FIX] product: lock uom in edition

On product packaging model, the uom is related to the product uom but
but editable. This can lead to some error in the database. This commit
set it as readonly to avoid any mistake.

Co-authored-by: Denis Roussel <840e652f0a1fd0b7a547b9df46f0bd1335dd20be@acsone.eu>

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