Bump langchain in /End_to_end_Solutions/AOAISearchDemo/app

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.0.139 to 0.3.7.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@v0.0.139...langchain==0.3.7)

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

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

End_to_end_Solutions/AOAISearchDemo/app/requirements.txt

@@ -6,7 +6,7 @@ azure-keyvault-secrets==4.7.0
 azure-search-documents==11.4.0b6
 azure-storage-blob==12.14.1
 Flask==2.2.2
-langchain==0.0.139
+langchain==0.3.7
 openai==0.27.4
 opencensus==0.11.2
 opencensus-ext-azure==1.1.9