Bump katex in /extensions/ql-vscode in the npm_and_yarn group

Bumps the npm_and_yarn group in /extensions/ql-vscode with 1 update: [katex](https://github.com/KaTeX/KaTeX).


Updates `katex` from 0.16.18 to 0.16.21
- [Release notes](https://github.com/KaTeX/KaTeX/releases)
- [Changelog](https://github.com/KaTeX/KaTeX/blob/main/CHANGELOG.md)
- [Commits](KaTeX/KaTeX@v0.16.18...v0.16.21)

---
updated-dependencies:
- dependency-name: katex
  dependency-type: indirect
  dependency-group: npm_and_yarn
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]