Bump postcss from 8.4.33 to 8.5.10 in /demo/frontend

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.33 to 8.5.10.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.4.33...8.5.10)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.10
  dependency-type: direct:development
...

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

demo/frontend/package.json

@@ -68,7 +68,7 @@
     "eslint-plugin-react-hooks": "^4.6.0",
     "eslint-plugin-react-refresh": "^0.4.3",
     "invariant": "^2.2.4",
-    "postcss": "^8.4.28",
+    "postcss": "^8.5.10",
     "postinstall-postinstall": "^2.1.0",
     "prettier": "^3.0.3",
     "relay-compiler": "^16.2.0",