docs: fix ReferenceError in open-redirect example (Url -> URL) (#2465)

Author: ofri-peretz

src/content/pages/en/advanced/best-practice-security.mdx

@@ -64,7 +64,7 @@ Here is an example of checking URLs before using `res.redirect` or `res.location
 ```js
 app.use((req, res) => {
   try {
-    if (new Url(req.query.url).host !== 'example.com') {
+    if (new URL(req.query.url).host !== 'example.com') {
       return res.status(400).end(`Unsupported redirect to host: ${req.query.url}`);
     }
   } catch (e) {