Bump next from 14.0.1 to 15.1.1 in /chapter4/next-example-app

Bumps [next](https://github.com/vercel/next.js) from 14.0.1 to 15.1.1.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v14.0.1...v15.1.1)

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

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

Author: dependabot[bot]