[mdx] remove mention of layout frontmatter property (#9474)

Co-authored-by: Armand Philippot <[email protected]>

src/content/docs/en/guides/integrations-guide/mdx.mdx

@@ -100,7 +100,7 @@ MDX supports using `export` statements to add variables to your MDX content or t
 
 For example, you can export a `title` field from an MDX page or component to use as a heading with `{JSX expressions}`:
 
-```mdx title="/src/pages/posts/post-1.mdx"
+```mdx title="/src/blog/posts/post-1.mdx"
 export const title = 'My first MDX post'
 
 # {title}
@@ -132,13 +132,15 @@ The following properties are available to a `.astro` component when using an `im
 
 The Astro MDX integration includes support for using frontmatter in MDX by default. Add frontmatter properties just as you would in Markdown files, and these variables are available to use in the template, and as named properties when importing the file somewhere else.
 
-```mdx title="/src/pages/posts/post-1.mdx"
+```mdx title="/src/blog/posts/post-1.mdx"
 ---
-layout: '../../layouts/BlogPostLayout.astro'
 title: 'My first MDX post'
+author: 'Houston'
 ---
 
 # {frontmatter.title}
+
+Written by: {frontmatter.author}
 ```
 
 ### Using Components in MDX
@@ -149,22 +151,18 @@ Don't forget to include a `client:directive` on your UI framework components, if
 
 See more examples of using import and export statements in the [MDX docs](https://mdxjs.com/docs/what-is-mdx/#esm).
 
-```mdx title="src/pages/about.mdx" {5-6} /<.+\/>/
+```mdx title="src/blog/post-1.mdx" {4,9}
 ---
-layout: ../layouts/BaseLayout.astro
-title: About me
+title: My first post
 ---
-import Button from '../components/Button.astro';
 import ReactCounter from '../components/ReactCounter.jsx';
 
-I live on **Mars** but feel free to <Button title="Contact me" />.
+I just started my new Astro blog! 
 
 Here is my counter component, working in MDX:
-
 <ReactCounter client:load />
 ```
 
-
 #### Custom components with imported MDX
 
 When rendering imported MDX content, [custom components](#assigning-custom-components-to-html-elements) can be passed via the `components` prop.
@@ -188,7 +186,7 @@ With MDX, you can map Markdown syntax to custom components instead of their stan
 
 Import your custom component into your `.mdx` file, then export a `components` object that maps the standard HTML element to your custom component:
 
-```mdx title="src/pages/about.mdx"
+```mdx title="src/blog/posts/post-1.mdx"
 import Blockquote from '../components/Blockquote.astro';
 export const components = {blockquote: Blockquote}