Remove use of deprecated OpenAI models

[vblagoje]

Summary

In light of the recent announcement by OpenAI about the shutdown of several models in early January 2024, we need to update our usage of these models in Haystack.

Affected Models

See https://openai.com/blog/gpt-4-api-general-availability for more details

Proposed Changes

To address this, the following updates are proposed:

1. Identify alternative models that can replace the deprecated ones. -> gpt-3.5-turbo-instruct
2. Update the codebase to integrate these new models.
3. Update tutorials: https://github.com/search?q=repo%3Adeepset-ai%2Fhaystack-tutorials+davinci&type=code

Timeline

Given the urgency, the proposed timeline for these updates is latest January 4th