Docs: Make "With URL Obeject" only displayed in Pages docs (#65547)

App router [does not
support](https://nextjs.org/docs/messages/app-dir-dynamic-href) dynamic
hrefs: removing it from the app router docs, and only having it in the
pages router docs.

Fixes #65505

---------

Co-authored-by: samcx <sam@vercel.com>

docs/02-app/02-api-reference/01-components/link.mdx

@@ -393,6 +393,8 @@ function Home() {
 export default Home
 ```
 
+<PagesOnly>
+
 ### With URL Object
 
 `Link` can also receive a URL object and it will automatically format it to create the URL string. Here's how to do it:
@@ -437,6 +439,8 @@ The above example has a link to:
 
 You can use every property as defined in the [Node.js URL module documentation](https://nodejs.org/api/url.html#url_url_strings_and_url_objects).
 
+</PagesOnly>
+
 ### Replace the URL instead of push
 
 The default behavior of the `Link` component is to `push` a new URL into the `history` stack. You can use the `replace` prop to prevent adding a new entry, as in the following example: