website: bump katex from 0.16.11 to 0.16.21 in /website (#12731)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

website/package-lock.json

@@ -12616,9 +12616,9 @@
             }
         },
         "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"