Bump next from 14.2.15 to 14.2.21 in /examples/with-clerk

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] <support@github.com>

examples/with-clerk/package.json

@@ -10,7 +10,7 @@
     "@types/node": "20.1.3",
     "@types/react": "18.2.6",
     "@types/react-dom": "18.2.4",
-    "next": "14.2.15",
+    "next": "14.2.21",
     "react": "18.2.0",
     "react-dom": "18.2.0",
     "typescript": "5.0.4"