Bump katex from 0.15.3 to 0.15.6 (#577)

Bump katex from 0.15.3 to 0.15.6 (#577)

Bumps [katex](https://github.com/KaTeX/KaTeX) from 0.15.3 to 0.15.6.
- [Release notes](https://github.com/KaTeX/KaTeX/releases)
- [Changelog](https://github.com/KaTeX/KaTeX/blob/main/CHANGELOG.md)
- [Commits](https://github.com/KaTeX/KaTeX/compare/v0.15.3...v0.15.6)

---
updated-dependencies:
- dependency-name: katex
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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