chore: Revert back langchain imports

Author: kiran-4444

portkey_ai/llms/langchain/chat.py

@@ -16,7 +16,7 @@
 
 try:
     from langchain.callbacks.manager import CallbackManagerForLLMRun
-    from langchain_community.chat_models.base import SimpleChatModel
+    from langchain.chat_models.base import SimpleChatModel
     from langchain.pydantic_v1 import Field, PrivateAttr
     from langchain.schema.messages import (
         AIMessage,

tests/test_llm_langchain.py

@@ -7,9 +7,9 @@
 
 from tests.utils import read_json_file
 from portkey_ai.langchain import LangchainCallbackHandler
-from langchain_community.chat_models import ChatOpenAI
+from langchain.chat_models import ChatOpenAI
 from langchain_core.prompts import ChatPromptTemplate
-from langchain_classic.chains import LLMChain
+from langchain.chains import LLMChain
 
 api_key = os.environ.get("PORTKEY_API_KEY")