Add missing imports from astro:content (#2636)

src/pages/en/guides/rss.mdx

@@ -96,6 +96,7 @@ export async function get(context) {
 You can configure your collection schema to enforce these expected RSS properties. Import and apply `rssSchema` to ensure that each collection entry produces a valid RSS feed item.
 
 ```js title="src/content/config.ts" "rssSchema"
+import { defineCollection } from 'astro:content';
 import { rssSchema } from '@astrojs/rss';
 
 const blog = defineCollection({
@@ -147,8 +148,9 @@ Whenever you're using HTML content in XML, we suggest using a package like [`san
 
 When using content collections, render the post `body` using a standard Markdown parser like [`markdown-it`](https://github.com/markdown-it/markdown-it) and sanitize the result:
 
-```js title="src/pages/rss.xml.js" ins={2, 3, 4, 15}
+```js title="src/pages/rss.xml.js" ins={3, 4, 5, 16}
 import rss from '@astrojs/rss';
+import { getCollection } from 'astro:content';
 import sanitizeHtml from 'sanitize-html';
 import MarkdownIt from 'markdown-it';
 const parser = new MarkdownIt();