chore(deps)(deps-dev): bump @next/mdx from 15.5.4 to 16.0.3

Bumps [@next/mdx](https://github.com/vercel/next.js/tree/HEAD/packages/next-mdx) from 15.5.4 to 16.0.3.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](https://github.com/vercel/next.js/commits/v16.0.3/packages/next-mdx)

---
updated-dependencies:
- dependency-name: "@next/mdx"
  dependency-version: 16.0.3
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Author: dependabot[bot]