Bump next from 12.1.6 to 15.5.14 in /examples/next-js (#450)

Bumps [next](https://github.com/vercel/next.js) from 12.1.6 to 15.5.14.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v12.1.6...v15.5.14)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.14
  dependency-type: direct:production
...

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

Author: dependabot[bot]

examples/next-js/package.json

@@ -12,7 +12,7 @@
   "dependencies": {
     "gl-react": "5.2.0",
     "gl-react-dom": "5.2.0",
-    "next": "12.1.6",
+    "next": "15.5.14",
     "react": "18.1.0",
     "react-dom": "18.1.0"
   }