Bump langchain from 0.3.4 to 0.3.9

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.3.4 to 0.3.9.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==0.3.4...langchain==0.3.9)

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

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

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ amqp==5.2.0
 beautifulsoup4==4.12.3
 boto3==1.35.49
 imbalanced-learn==0.12.4
-langchain==0.3.4
+langchain==0.3.9
 langchain-anthropic==0.2.3
 langchain-community==0.3.3
 langchain-google-genai==2.0.1