[FIX] website_sale: accessories button no all width

The cell containing "Add to Cart" button that adds suggested accessories
in the cart has col-* classes. Thus it there is "flex-item" CSS
properties that make no sense since there is no container and the
sibling are not flex items.

So the button tried to take 100% of width and this commit just fix its
proposed width to 25%. Before change width was 16.7% width for large
screen, 25% for medium screen and 33.3% for small screen. I choosed 25%
since it seemed a good default (we don't need 33.3% since .btn is
whitespace:nowrap so the size will be higher than 25% if necessary).

opw-1914994
closes #29287

addons/website_sale/views/templates.xml

@@ -956,7 +956,7 @@
                             </t>
                             <span t-field="product.website_price" style="white-space: nowrap;" t-options="{'widget': 'monetary','display_currency': website.currency_id}" />
                         </td>
-                        <td class="col-lg-2 col-md-3 col-4 text-center">
+                        <td class="w-25 text-center">
                             <input class="js_quantity" name="product_id" t-att-data-product-id="product.id" type="hidden" />
                             <a role="button" class="btn btn-link js_add_suggested_products">
                                 <strong>Add to Cart</strong>