Bump next in /ai/gen-ai-agents/Document Understanding MCP AI Agent/files

Bumps [next](https://github.com/vercel/next.js) from 15.3.1 to 15.4.2.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.3.1...v15.4.2)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.4.2
  dependency-type: direct:production
...

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

Author: dependabot[bot]