Bump next from 15.1.5 to 15.2.3 in /examples/example_next

Bumps [next](https://github.com/vercel/next.js) from 15.1.5 to 15.2.3.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.1.5...v15.2.3)

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

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

Author: dependabot[bot]

examples/example_next/package.json

@@ -26,7 +26,7 @@
     "@fontsource/poppins": "^5.1.1",
     "@tailwindcss/typography": "^0.5.16",
     "firebase": "^10.14.1",
-    "next": "15.1.5",
+    "next": "15.2.3",
     "nextjs-toploader": "^3.7.15",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",