Bump @astrojs/mdx from 4.3.7 to 4.3.9

Bumps [@astrojs/mdx](https://github.com/withastro/astro/tree/HEAD/packages/integrations/mdx) from 4.3.7 to 4.3.9.
- [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/@astrojs/mdx@4.3.9/packages/integrations/mdx)

---
updated-dependencies:
- dependency-name: "@astrojs/mdx"
  dependency-version: 4.3.9
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -35,7 +35,7 @@
   },
   "devDependencies": {
     "@astrojs/check": "^0.9.4",
-    "@astrojs/mdx": "^4.3.7",
+    "@astrojs/mdx": "^4.3.9",
     "@astrojs/partytown": "^2.1.4",
     "@astrojs/tailwind": "^6.0.2",
     "@eslint/js": "^9.37.0",