Bump postcss from 8.4.5 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.5 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@8.4.5...8.4.31)

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

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -18,7 +18,7 @@
     "eslint-plugin-mirego": "0.0.1",
     "eslint-plugin-node": "^11.1.0",
     "eslint-plugin-promise": "^5.2.0",
-    "postcss": ">=8.2.13",
+    "postcss": ">=8.4.31",
     "prettier": "2.5.1",
     "stylelint": "13.13.1",
     "stylelint-config-mirego": "2.0.0",