Bump @astrojs/mdx from 4.3.9 to 4.3.12

Bumps [@astrojs/mdx](https://github.com/withastro/astro/tree/HEAD/packages/integrations/mdx) from 4.3.9 to 4.3.12.
- [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@4.3.12/packages/integrations/mdx)

---
updated-dependencies:
- dependency-name: "@astrojs/mdx"
  dependency-version: 4.3.12
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -51,7 +51,7 @@
   },
   "dependencies": {
     "@astrojs/check": "0.9.5",
-    "@astrojs/mdx": "4.3.9",
+    "@astrojs/mdx": "4.3.12",
     "@astrojs/preact": "4.1.2",
     "@astrojs/rss": "4.0.13",
     "@astrojs/sitemap": "^3.6.0",