[FIX] website_sale_coupon: new class for product results

For the tests on coupon on enterprise, there is a need of a new class to wait
search results to be loaded, or it would click on the /shop product instead of
waiting, resulting in a conccurent update error.

This closes #22263

addons/website_sale/views/templates.xml

@@ -164,7 +164,7 @@
             <t t-set="additional_title">Shop</t>
             <div id="wrap" class="js_sale">
                 <div class="oe_structure" />
-                <div class="container oe_website_sale">
+                <div t-attf-class="container oe_website_sale #{'oe_website_sale_search' if search else None}">
                     <div class="products_pager">
                         <div class="row" style="width: 100%;">
                             <t t-call="website_sale.search">