fix(mdx): fix for html multi-line comments

[slorber]

Motivation

Fix #9084

Test Plan

Dogfood on preview shouldn't crash at build time

https://deploy-preview-9100--docusaurus-2.netlify.app/tests/pages/markdown-tests-md

https://deploy-preview-9100--docusaurus-2.netlify.app/tests/pages/markdown-tests-mdx

[netlify]

✅ [V2]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 88	🟢 97	🟢 92	🟢 100	🟠 89	Report
/docs/installation	🟠 75	🟢 100	🟢 92	🟢 100	🟠 89	Report

[github-actions]

Size Change: 0 B

Total Size: 1.1 MB

ℹ️ View Unchanged

Filename	Size
website/.docusaurus/globalData.json	117 kB
website/build/assets/css/styles.********.css	113 kB
website/build/assets/js/main.********.js	828 kB
website/build/index.html	41 kB

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