build(deps): bump katex from 0.16.11 to 0.16.21 in /frontend

Bumps [katex](https://github.com/KaTeX/KaTeX) from 0.16.11 to 0.16.21.
- [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/v0.16.11...v0.16.21)

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

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

frontend/package-lock.json

@@ -5661,14 +5661,13 @@
       }
     },
     "node_modules/katex": {
-      "version": "0.16.11",
-      "resolved": "https://registry.npmjs.org/katex/-/katex-0.16.11.tgz",
-      "integrity": "sha512-RQrI8rlHY92OLf3rho/Ts8i/XvjgguEjOkO1BEXcU3N8BqPpSzBNwV/G0Ukr+P/l3ivvJUE/Fa/CwbS6HesGNQ==",
+      "version": "0.16.21",
+      "resolved": "https://registry.npmjs.org/katex/-/katex-0.16.21.tgz",
+      "integrity": "sha512-XvqR7FgOHtWupfMiigNzmh+MgUVmDGU2kXZm899ZkPfcuoPuFxyHmXsgATDpFZDAXCI8tvinaVcDo8PIIJSo4A==",
       "funding": [
         "https://opencollective.com/katex",
         "https://github.com/sponsors/katex"
       ],
-      "license": "MIT",
       "dependencies": {
         "commander": "^8.3.0"
       },