Upgrading @astrojs/mdx from 0.9.0 to 0.10.x breaks custom syntax highlighter that uses title metadata

[eliasbrange]

What version of astro are you using?

1.0.0

Are you using an SSR adapter? If so, which one?

None

What package manager are you using?

yarn

What operating system are you using?

Windows (WSL 2)

Describe the Bug

Upgrading @astrojs/mdx from 0.9.0 to 0.10.x breaks the line highlighter in rehype-pretty-code. It uses metadata in the title such as

```typescript {1, 5-6}

Since I do not use the built-in astro highlighter, my guess is that rehypeRaw, which was added as default with the same PR (https://github.com/withastro/astro/pull/4292) is causing some problems for me.

Working example (with @astrojs/mdx 0.9.0: https://stackblitz.com/edit/github-iyfzcn-zhr6ov

Non-working example (with @astrojs/mdx 0.10.1: https://stackblitz.com/edit/github-iyfzcn

Link to Minimal Reproducible Example

https://stackblitz.com/edit/github-iyfzcn

Participation

• [ ] I am willing to submit a pull request for this issue.