Update requirements.txt

Resolve runtime error by installing langchain-community, several dependencies require update, should be automatically updated after refresh, have space successfully running as a duplicate but unable to test due to API login needed. If issue persists, add "langchain" as first line requirement, having langchain-community as second requirement.

requirements.txt

@@ -1,4 +1,4 @@
-langchain
+langchain-community>=0.3.16
 openai>=0.27.0
 pypdf
 deeplake