Bump @astrojs/mdx from 4.2.0 to 4.2.1

Bumps [@astrojs/mdx](https://github.com/withastro/astro/tree/HEAD/packages/integrations/mdx) from 4.2.0 to 4.2.1.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/integrations/mdx/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/astro@4.2.1/packages/integrations/mdx)

---
updated-dependencies:
- dependency-name: "@astrojs/mdx"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package.json

@@ -13,7 +13,7 @@
   "dependencies": {
     "@astro-community/astro-embed-youtube": "^0.5.6",
     "@astrojs/check": "^0.9.4",
-    "@astrojs/mdx": "^4.1.0",
+    "@astrojs/mdx": "^4.2.1",
     "@astrojs/react": "^4.2.1",
     "@astrojs/sitemap": "^3.2.1",
     "@astrojs/tailwind": "^5.1.4",