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:development
...

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

Author: dependabot[bot]

website/package-lock.json

@@ -47,7 +47,7 @@
     "@tailwindcss/forms": "^0.5.3",
     "@tailwindcss/typography": "^0.5.9",
     "autoprefixer": "^10.4.13",
-    "postcss": "^8.4.21",
+    "postcss": "^8.4.31",
     "prettier": "^3.0.2",
     "tailwindcss": "^3.2.6"
   }