Bump postcss from 8.4.5 to 8.4.31 in /examples/cms-prepr

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]>

Author: dependabot[bot]

examples/cms-prepr/package.json

@@ -14,7 +14,7 @@
   },
   "devDependencies": {
     "autoprefixer": "10.4.2",
-    "postcss": "8.4.5",
+    "postcss": "8.4.31",
     "tailwindcss": "^3.0.15"
   }
 }