docs: remove outdated section from SEO docs (#11472)

documentation/docs/40-best-practices/20-seo.md

@@ -14,7 +14,7 @@ While search engines have got better in recent years at indexing content that wa
 
 ### Performance
 
-Signals such as [Core Web Vitals](https://web.dev/vitals/#core-web-vitals) impact search engine ranking. Because Svelte and SvelteKit introduce minimal overhead, it's easier to build high performance sites. You can test your site's performance using Google's [PageSpeed Insights](https://pagespeed.web.dev/) or [Lighthouse](https://developers.google.com/web/tools/lighthouse).
+Signals such as [Core Web Vitals](https://web.dev/vitals/#core-web-vitals) impact search engine ranking. Because Svelte and SvelteKit introduce minimal overhead, it's easier to build high performance sites. You can test your site's performance using Google's [PageSpeed Insights](https://pagespeed.web.dev/) or [Lighthouse](https://developers.google.com/web/tools/lighthouse). Read [the performance page](performance) for more details.
 
 ### Normalized URLs
 
@@ -28,30 +28,6 @@ Every page should have well-written and unique `<title>` and `<meta name="descri
 
 > A common pattern is to return SEO-related `data` from page [`load`](load) functions, then use it (as [`$page.data`](modules#$app-stores)) in a `<svelte:head>` in your root [layout](routing#layout).
 
-### Structured data
-
-[Structured data](https://developers.google.com/search/docs/advanced/structured-data/intro-structured-data) helps search engines understand the content of a page. If you're using structured data alongside [`svelte-preprocess`](https://github.com/sveltejs/svelte-preprocess), you will need to explicitly preserve `ld+json` data (this [may change in future](https://github.com/sveltejs/svelte-preprocess/issues/305)):
-
-```js
-/// file: svelte.config.js
-// @filename: ambient.d.ts
-declare module 'svelte-preprocess';
-
-// @filename: index.js
-// ---cut---
-import preprocess from 'svelte-preprocess';
-
-/** @type {import('@sveltejs/kit').Config} */
-const config = {
-	preprocess: preprocess({
-		preserve: ['ld+json']
-		// ...
-	})
-};
-
-export default config;
-```
-
 ### Sitemaps
 
 [Sitemaps](https://developers.google.com/search/docs/advanced/sitemaps/build-sitemap) help search engines prioritize pages within your site, particularly when you have a large amount of content. You can create a sitemap dynamically using an endpoint: