Bump nanoid and ai in /samples/vllm/ui

Bumps [nanoid](https://github.com/ai/nanoid) to 3.3.8 and updates ancestor dependency [ai](https://github.com/vercel/ai). These dependencies need to be updated together.


Updates `nanoid` from 3.3.7 to 3.3.8
- [Release notes](https://github.com/ai/nanoid/releases)
- [Changelog](https://github.com/ai/nanoid/blob/main/CHANGELOG.md)
- [Commits](ai/nanoid@3.3.7...3.3.8)

Updates `ai` from 2.2.36 to 4.0.18
- [Release notes](https://github.com/vercel/ai/releases)
- [Changelog](https://github.com/vercel/ai/blob/main/CHANGELOG.md)
- [Commits](https://github.com/vercel/ai/compare/[email protected]@4.0.18)

---
updated-dependencies:
- dependency-name: nanoid
  dependency-type: indirect
- dependency-name: ai
  dependency-type: direct:production
...

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