chore(deps): bump postcss from 8.4.25 to 8.4.31 in /docs

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.25 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@8.4.25...8.4.31)

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

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

docs/package.json

@@ -34,7 +34,7 @@
     "medium-zoom": "^1.0.8",
     "node-fetch": "^3.3.1",
     "path-browserify": "^1.0.1",
-    "postcss": "^8.4.24",
+    "postcss": "^8.4.31",
     "prism-react-renderer": "^1.3.5",
     "react": "^17.0.2",
     "react-dom": "^17.0.2",