chore(deps): Bump langchain from 0.3.0 to 0.3.1 in /examples/functions

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.3.0 to 0.3.1.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==0.3.0...langchain==0.3.1)

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

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

examples/functions/requirements.txt

@@ -1,2 +1,2 @@
-langchain==0.3.0
+langchain==0.3.1
 openai==1.47.1