community[patch]: Update root_validators to use pre=True or pre=False (#23731)

Update root_validators in preparation for pydantic 2 migration.

libs/community/langchain_community/agents/openai_assistant/base.py

@@ -209,7 +209,7 @@ class OpenAIAssistantV2Runnable(OpenAIAssistantRunnable):
     as_agent: bool = False
     """Use as a LangChain agent, compatible with the AgentExecutor."""
 
-    @root_validator()
+    @root_validator(pre=False, skip_on_failure=True)
     def validate_async_client(cls, values: dict) -> dict:
         if values["async_client"] is None:
             import openai