chore(deps): Bump next in /examples/next/custom-toolbar (#2125)

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
...

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