`ChatGroq` errors on multiple submissions

[cpsievert]

Seems chatlas needs workarounds similar to tidyverse/ellmer#224

from chatlas import ChatGroq

chat = ChatGroq()
chat.chat("Tell me about New Zealand?")
chat.chat("What's its capital?")

openai.BadRequestError: Error code: 400 - {'error': {'message': "'messages.1' : for 'role:assistant' the following must be satisfied[('messages.1.content' : value must be a string)]", 'type': 'invalid_request_error'}}