Bump postcss from 8.4.13 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.13 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/8.4.13...8.4.31)

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

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

package.json

@@ -30,7 +30,7 @@
     "eslint-config-next": "12.0.7",
     "jest": "27.4.4",
     "jest-watch-typeahead": "0.6.1",
-    "postcss": "8.4.13",
+    "postcss": "8.4.31",
     "react-collapsible": "2.8.4",
     "tailwindcss": "3.0.24",
     "typescript": "4.5.3"