Bump postcss from 8.4.23 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.23 to 8.4.31.
- [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/8.4.23...8.4.31)

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

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

package.json

@@ -63,7 +63,7 @@
     "eslint-plugin-promise": "^5.1.0",
     "eslint-plugin-react": "^7.23.2",
     "next-sitemap": "^1.6.203",
-    "postcss": "^8.4.20",
+    "postcss": "^8.4.31",
     "tailwindcss": "^3.3.2",
     "webpack-bundle-analyzer": "^4.5.0"
   },