Fix broken fragment link (#5200)

packages/integrations/mdx/README.md

@@ -194,8 +194,7 @@ export default {
 …every MDX file will have `customProperty` in its frontmatter! See [our Markdown documentation](https://docs.astro.build/en/guides/markdown-content/#injecting-frontmatter) for more usage instructions and a [reading time plugin example](https://docs.astro.build/en/guides/markdown-content/#example-calculate-reading-time).
 
 ### Layouts
-
-Layouts can be applied [in the same way as standard Astro Markdown](https://docs.astro.build/en/guides/markdown-content/#markdown-layouts). You can add a `layout` to [your frontmatter](#frontmatter) like so:
+Layouts can be applied [in the same way as standard Astro Markdown](https://docs.astro.build/en/guides/markdown-content/#frontmatter-layout). You can add a `layout` to [your frontmatter](#frontmatter) like so:
 
 ```yaml
 ---