chore(deps): Bump langchain from 0.2.3 to 0.2.7 in /examples/functions

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.2.3 to 0.2.7.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==0.2.3...langchain==0.2.7)

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

Signed-off-by: dependabot[bot] <support@github.com>

examples/functions/requirements.txt

@@ -1,2 +1,2 @@
-langchain==0.2.3
+langchain==0.2.7
 openai==1.33.0