chore(deps): bump rehype-mathjax from 5.0.0 to 6.0.0 (#745)

Bumps [rehype-mathjax](https://github.com/remarkjs/remark-math) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/remarkjs/remark-math/releases)
- [Commits](https://github.com/remarkjs/remark-math/compare/rehype-mathjax@5.0.0...rehype-mathjax@6.0.0)

---
updated-dependencies:
- dependency-name: rehype-mathjax
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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