[FIX] website_sale_stock: unicode as uom name will throw encode error

Before this commit, if you had an uom with an unicode character as name, it
would throws an UnicodeEncodeError.

Now, since the str() parsing is not needed, removing it fixes the issue

This closes #20325
This closes #21374

addons/website_sale_stock/controllers/main.py

@@ -3,6 +3,7 @@
 
 from odoo.addons.website_sale.controllers.main import WebsiteSale
 from odoo.http import request
+from odoo.tools import ustr
 from odoo.tools.pycompat import izip
 
 class WebsiteSale(WebsiteSale):
@@ -14,13 +15,13 @@ class WebsiteSale(WebsiteSale):
         for r, variant in izip(res, request.env['product.product'].sudo().browse(variant_ids)):
             r.extend([{
                 'virtual_available': variant.virtual_available,
-                'product_type': str(variant.type),
-                'inventory_availability': str(variant.inventory_availability),
+                'product_type': variant.type,
+                'inventory_availability': variant.inventory_availability,
                 'available_threshold': variant.available_threshold,
-                'custom_message': str(variant.custom_message),
+                'custom_message': variant.custom_message,
                 'product_template': variant.product_tmpl_id.id,
                 'cart_qty': variant.cart_qty,
-                'uom_name': str(variant.uom_id.name),
+                'uom_name': variant.uom_id.name,
             }])
 
         return res