Bump eslint-mdx from 2.2.0 to 3.1.5 (#7034)

Bumps [eslint-mdx](https://github.com/mdx-js/eslint-mdx) from 2.2.0 to 3.1.5.
- [Release notes](https://github.com/mdx-js/eslint-mdx/releases)
- [Changelog](https://github.com/mdx-js/eslint-mdx/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mdx-js/eslint-mdx/compare/eslint-mdx@2.2.0...eslint-mdx@3.1.5)

---
updated-dependencies:
- dependency-name: eslint-mdx
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>