fix(stripComments): properly pass in the micromark extensions

[maximilianfalco]

	Fix RM-XYZ

🧰 Changes

We saw that the stripComments pipeline was incorrectly parsing magic blocks with the mdxish flag. Turns out, it was just because we were calling unified().data twice, which caused the second call to overwrite the first one, which in this case replaced the magic block extension with the mdx expression extension

Before	After

🧬 QA & Testing

1. Have a page contain this

[block:html]
{
  "html": "<div>Hello</div>"
}
[/block]

2. View it as markdown
3. The returned markdown should be correct

• Broken on production.
• Working in this PR app.

[rafegoldberg]

This PR was released!

🚀 Changes included in v13.1.2