[FIX] point_of_sale: price list test

This commit fix the test when different localisation are used to make sure that the public pricelist is used.
Before, when pos_pricelist test was done and some localisation were installed, it could lead to test failure because the default pricelist wasn't correct on the partners.

closes odoo/odoo#109646

Signed-off-by: Trinh Jacky (trj) <trj@odoo.com>