Bump langchain from 0.2.14 to 0.2.15

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.2.14 to 0.2.15.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==0.2.14...langchain==0.2.15)

---
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]

poetry.lock

@@ -15,7 +15,7 @@ streamlit = "^1.37.1"
 azure-cosmos = "^4.7.0"
 plotly = "^5.23.0"
 pandas = "^2.2.2"
-langchain = "^0.2.14"
+langchain = "^0.2.15"
 langchain-openai = "^0.1.22"
 langchain-community = "^0.2.12"
 azure-search-documents = "^11.5.1"