chore(deps-dev): bump postcss from 8.4.14 to 8.4.31 (#495)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.14 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@8.4.14...8.4.31)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -50,7 +50,7 @@
     "eslint-plugin-mdx": "^2.0.1",
     "husky": "^8.0.1",
     "lint-staged": "^15.0.0",
-    "postcss": "^8.4.14",
+    "postcss": "^8.4.31",
     "prettier": "^2.7.0",
     "prism-react-renderer": "^1.3.3",
     "react": "^17.0.2",