chore(deps): Bump next in /examples/next/custom-toolbar

Bumps [next](https://github.com/vercel/next.js) from 14.2.26 to 15.3.3.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v14.2.26...v15.3.3)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.3.3
  dependency-type: direct:production
...

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

Author: dependabot[bot]