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

@@ -74,7 +74,7 @@
     "eslint-plugin-import": "^2.27.5",
     "eslint-plugin-react": "^7.32.1",
     "eslint-plugin-storybook": "^0.6.12",
-    "postcss": "^8.4.21",
+    "postcss": "^8.4.31",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
     "rollup": "^3.10.0",