[FIX] website_sale: correct 'border_primary' color

Some elements in the eCommerce are styled using the 'border_primary'
class. The color used by the class is however the wrong one, as it was
set to the odoo purple while it was meant to be the theme primary color.
This commit fixes the color.

Note that BS4 has an equivalent for that class (.border.border-primary)
but as this is a stable fix, it was not changed. It will be adapted in
master with https://github.com/odoo/odoo/pull/31147

closes odoo/odoo#31214

addons/website_sale/static/src/scss/website_sale.scss

@@ -597,7 +597,7 @@ td.noborder {
 }
 
 .border_primary {
-    border: 1px solid $o-brand-odoo;
+    border: 1px solid theme-color('primary');
 }
 
 .js_change_shipping {