Remove unused arguments from openai generate functions.

[HerrIvan]

Removes unused arguments in generate_base and generate_choice openai model functions.

• self.client was not necessary, as the function already uses a callable pointing to a method of the self.client instance.
• max_tokens is not used in generate_choice.
• reduces samples to 1 when calling the openai API in generate_choice, as discussed in Reduce token consumption for "choice" generation with openAI. #368 . This fix is not too relevant, as the extra token-cost generated per call was just samples-1, but it corrects the code. Note that the alternative solution suggested is not feasible: One can call the api in parallel, but only with a same prompt. As the different samples diverge, both prompts and masks do so, hence any parallelization should be upstream from the API call.

[rlouf]

Thank you! Can we go all the way and remove it from generate_base? Also we don't need the client to be a property of the class.

[HerrIvan]

• removed client from as an argument from generate_base, it somehow escaped me.
• removed as a property from the class. It is created but just stored in the closure.
• Warning: please check if y changes to these kind of arguments ( signature="(),(),(m),()->(s)" ) are ok.

[rlouf]

Thank you!