Bump next from 14.2.10 to 14.2.15 in /test/nextjs/app

Bumps [next](https://github.com/vercel/next.js) from 14.2.10 to 14.2.15.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v14.2.10...v14.2.15)

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

Signed-off-by: dependabot[bot] <support@github.com>

test/nextjs/app/package.json

@@ -9,7 +9,7 @@
   },
   "dependencies": {
     "@appsignal/nodejs": "^3.0.26",
-    "next": "^14.2.10",
+    "next": "^14.2.15",
     "react": "^18.2.0",
     "react-dom": "^18.2.0"
   },