docs: fix sitemap namespace (#14918)

Author: wobedi

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

@@ -39,12 +39,12 @@ export async function GET() {
 		`
 		<?xml version="1.0" encoding="UTF-8" ?>
 		<urlset
-			xmlns="https://www.sitemaps.org/schemas/sitemap/0.9"
-			xmlns:xhtml="https://www.w3.org/1999/xhtml"
-			xmlns:mobile="https://www.google.com/schemas/sitemap-mobile/1.0"
-			xmlns:news="https://www.google.com/schemas/sitemap-news/0.9"
-			xmlns:image="https://www.google.com/schemas/sitemap-image/1.1"
-			xmlns:video="https://www.google.com/schemas/sitemap-video/1.1"
+			xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
+			xmlns:xhtml="http://www.w3.org/1999/xhtml"
+			xmlns:mobile="http://www.google.com/schemas/sitemap-mobile/1.0"
+			xmlns:news="http://www.google.com/schemas/sitemap-news/0.9"
+			xmlns:image="http://www.google.com/schemas/sitemap-image/1.1"
+			xmlns:video="http://www.google.com/schemas/sitemap-video/1.1"
 		>
 			<!-- <url> elements go here -->
 		</urlset>`.trim(),