Bump langchain-openai from 0.3.18 to 0.3.21 (camel-ai#569)

Bumps [langchain-openai](https://github.com/langchain-ai/langchain) from 0.3.18 to 0.3.21.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain-openai==0.3.18...langchain-openai==0.3.21)

---
updated-dependencies:
- dependency-name: langchain-openai
  dependency-version: 0.3.21
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]