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](https://github.com/postcss/postcss/compare/8.4.21...8.4.31)

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

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

package.json

@@ -77,7 +77,7 @@
 		"eslint-config-next": "13.4.11-canary.1",
 		"jest-mock-extended": "^3.0.3",
 		"next-unused": "0.0.6",
-		"postcss": "^8.4.21",
+		"postcss": "^8.4.31",
 		"postcss-flexbugs-fixes": "^5.0.2",
 		"postcss-hover-media-feature": "^1.0.2",
 		"postcss-nested": "^6.0.1",