Fix incorrect type issues in conversation models methods

[blenderskool]

Change Summary

Fixed following TypeScript related issues:

• .conversations().models() was returning a union type that wasn't overloaded on the id param it accepts similar to other methods in the Typesense client.
• .conversations().models().retrieve() was returning an incorrect type as { models: ConversationModelSchema[] } but from my tests it actually just returns an array of the model schemas.

PR Checklist

• [x] I have read and signed the Contributor License Agreement.

[jasonbosco]

Thanks @blenderskool

Could you complete the CLA and complete the PR Checklist in the PR description?

[blenderskool]

Done @jasonbosco