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:development
...

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

package.json

@@ -66,7 +66,7 @@
     "eslint": "8.37.0",
     "eslint-config-xo": "0.43.1",
     "eslint-plugin-unicorn": "46.0.0",
-    "postcss": "8.4.21"
+    "postcss": "8.4.31"
   },
   "peerDependencies": {
     "postcss": ">=8.0.0"