Bump langchain from 0.0.334 to 0.0.340

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.0.334 to 0.0.340.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](https://github.com/langchain-ai/langchain/compare/v0.0.334...v0.0.340)

---
updated-dependencies:
- dependency-name: langchain
dependency-type: direct:production
update-type: version-update:semver-patch
...

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

requirements.txt

@@ -1,6 +1,6 @@
 anthropic==0.5.0
 faiss-cpu==1.7.4
-langchain==0.0.334
+langchain==0.0.340
 langsmith==0.0.63
 numpy>=1.22.2 # not directly required, pinned by Snyk to avoid a vulnerability
 openai==0.28.1