Add missing langchain dependencies (#4208)

* Add missing langchain dependencies

* Import HumanInputLLM from langchain_community

bugbug/generative_model_tool.py

@@ -6,7 +6,7 @@
 from abc import ABC, abstractmethod
 from typing import Any
 
-from langchain.llms.human import HumanInputLLM
+from langchain_community.llms import HumanInputLLM
 from langchain_openai import ChatOpenAI
 
 from bugbug.utils import get_secret

requirements.txt

@@ -2,6 +2,9 @@ amqp==5.2.0
 beautifulsoup4==4.12.3
 boto3==1.34.108
 imbalanced-learn==0.12.2
+langchain==0.2.1
+langchain-community==0.2.1
+langchain-openai==0.1.8
 libmozdata==0.2.4
 lmdb==1.4.1
 markdown2==2.4.13