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:development
  update-type: version-update:semver-patch
...
Signed-off-by: dependabot[bot] <support@github.com>