deps(example): bump the dependencies group

Bumps the dependencies group in /examples/nextjs-14-app-dir-validate-email with 2 updates: [@types/react](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/react) and [postcss](https://github.com/postcss/postcss).


Updates `@types/react` from 18.2.51 to 18.2.54
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/react)

Updates `postcss` from 8.4.33 to 8.4.34
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.33...8.4.34)

---
updated-dependencies:
- dependency-name: "@types/react"
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: dependencies
- dependency-name: postcss
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: dependencies
...

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

examples/nextjs-14-app-dir-validate-email/package.json

@@ -16,7 +16,7 @@
   },
   "devDependencies": {
     "@types/node": "^20",
-    "@types/react": "18.2.51",
+    "@types/react": "18.2.54",
     "@types/react-dom": "^18",
     "autoprefixer": "^10.4.17",
     "eslint": "^8",