Fix param object key in content-collections.mdx

The sample as-is resulted in the error "[ERROR] Missing parameter: post"

src/content/docs/en/guides/content-collections.mdx

@@ -515,7 +515,7 @@ import { getCollection, render } from 'astro:content';
 export async function getStaticPaths() {
   const posts = await getCollection('blog');
   return posts.map(post => ({
-    params: { id: post.id },
+    params: { post: post.id },
     props: { post },
   }));
 }