Bump katex in /app in the npm_and_yarn group across 1 directory

Bumps the npm_and_yarn group with 1 update in the /app directory: [katex](https://github.com/KaTeX/KaTeX).


Updates `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
  dependency-group: npm_and_yarn
...

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

app/package-lock.json

@@ -3380,14 +3380,13 @@
       }
     },
     "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"
       },