OpenAI's beta parse call is broken with our Libretto wrapper

[james-deee]

OpenAI has a new "parse" call that you can call that will return some parsed data according to your json schema: https://platform.openai.com/docs/guides/structured-outputs/how-to-use

You can try this out in examples/simple.ts and just change the "originalOpenai" to be "openai" (which is the libretto one), and you'll get a type error. I think we need to override something, but I didn't want to go down a rabbit hole at the moment.