Bump langchain from 0.0.240 to 0.0.254

Bumps [langchain](https://github.com/hwchase17/langchain) from 0.0.240 to 0.0.254.
- [Release notes](https://github.com/hwchase17/langchain/releases)
- [Commits](https://github.com/hwchase17/langchain/compare/v0.0.240...v0.0.254)

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

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

requirements.txt

@@ -1,6 +1,6 @@
 transformers
 openai
-langchain==0.0.240
+langchain==0.0.254
 
 torch
 torchvision