edit(beta) functionality no longer working: due to deprecated model

[ivy-rew]

Similar problem as with #42

{
  "error" : {
    "message" : "The model `code-davinci-edit-001` has been deprecated, learn more here: https://platform.openai.com/docs/deprecations",
    "type" : "invalid_request_error",
    "param" : null,
    "code" : "model_not_found"
  }
}

I think the idea of the 'beta' editing was to allow prompts with other models than davinci-3.5. Since #42, this is no longer necessary, as the model is selectable for the user. I'd drop that feature ... or allow a "seconary-model" selection, which is in charge when running the "edit" prompt.

[ivy-rew]

fyi @ivy-sgi