chore(deps): Bump langchain from 0.1.20 to 0.3.0 in /examples/langchain

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.1.20 to 0.3.0.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==0.1.20...langchain==0.3.0)

---
updated-dependencies:
- dependency-name: langchain
  dependency-type: direct:production
...

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

Author: dependabot[bot]

examples/langchain/requirements.txt

@@ -1,7 +1,7 @@
 streamlit==1.34.0
 pandas==2.2.2
 python-dotenv==1.0.1
-langchain==0.1.20
+langchain==0.3.0
 pathlib==1.0.1
 PyJWT==2.8.0
 openai==1.30.1