chore(deps): bump postcss from 8.4.21 to 8.4.31 in /website

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.21 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.21...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:production
...

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

website/package.json

@@ -24,7 +24,7 @@
     "ace-builds": "^1.9.5",
     "autoprefixer": "^10.4.8",
     "clsx": "^1.2.1",
-    "postcss": "^8.4.16",
+    "postcss": "^8.4.31",
     "prism-react-renderer": "^1.3.5",
     "react": "^17.0.2",
     "react-ace": "^10.1.0",