[FIX] point_of_sale: missing currency symbol on receipts

- Buy anything with de POS and generate a receipt.

Before this commit:

The currency symbol is missing everywhere.

After this commit:

The currency symbol is present next to any price.

closes odoo/odoo#38464

Opw: 2083186
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>