Bump langsmith from 0.7.16 to 0.8.18 in /ai/langchain-skills-agent/src

Bumps [langsmith](https://github.com/langchain-ai/langsmith-sdk) from 0.7.16 to 0.8.18.
- [Release notes](https://github.com/langchain-ai/langsmith-sdk/releases)
- [Commits](langchain-ai/langsmith-sdk@v0.7.16...v0.8.18)

---
updated-dependencies:
- dependency-name: langsmith
  dependency-version: 0.8.18
  dependency-type: indirect
...

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Author: dependabot[bot]