Bump next from 14.2.15 to 14.2.21 in /example/next (#165)

Bumps [next](https://github.com/vercel/next.js) from 14.2.15 to 14.2.21.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v14.2.15...v14.2.21)

---
updated-dependencies:
- dependency-name: next
  dependency-type: direct:production
...

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

example/next/package.json

@@ -14,7 +14,7 @@
     "i18next-chained-backend": "4.6.2",
     "i18next-http-backend": "2.5.1",
     "i18next-localstorage-backend": "4.2.0",
-    "next": "14.2.15",
+    "next": "14.2.21",
     "next-i18next": "15.3.0"
   },
   "devDependencies": {