deps: bump @mdx-js/mdx from 1.6.22 to 2.2.1 in /theme (#397)

Bumps [@mdx-js/mdx](https://github.com/mdx-js/mdx/tree/HEAD/packages/mdx) from 1.6.22 to 2.2.1. - [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/2.2.1/packages/mdx) --- updated-dependencies: - dependency-name: "@mdx-js/mdx" dependency-type: direct:production update-type: version-update:semver-major ... Signed-off-by: dependabot[bot] <support@github.com> Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>