build(deps): bump @mdx-js/mdx from 1.6.18 to 1.6.22 in /docs

Bumps [@mdx-js/mdx](https://github.com/mdx-js/mdx/tree/HEAD/packages/mdx) from 1.6.18 to 1.6.22.
- [Release notes](https://github.com/mdx-js/mdx/releases)
- [Changelog](https://github.com/mdx-js/mdx/blob/main/changelog.md)
- [Commits](https://github.com/mdx-js/mdx/commits/v1.6.22/packages/mdx)

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

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