build(deps): bump postcss from 8.4.21 to 8.4.31

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>

apps/next-preview/package.json

@@ -13,7 +13,7 @@
     "@c6r/react": "workspace:*",
     "autoprefixer": "^10.4.13",
     "next": "13.3.0",
-    "postcss": "^8.4.21",
+    "postcss": "^8.4.31",
     "react": "18.2.0",
     "react-dom": "18.2.0",
     "tailwindcss": "^3.2.6"