Continue Cohere support updates

[jmartin-tech]

#1252 update the library dependency for cohere, further updates to convert all request to use the new ClientV2 objects are needed.

Additionally the following header warning is seen with the default command model selected.

"x-api-warning": "model 'command' is deprecated. Please consider upgrading to a newer model to avoid future service disruptions"

And when utilizing the legacy v1 Client object responses to generate() also include a header warning is reported:

"x-api-warning": "unknown field: parameter 'model' is not a valid field"

[jmartin-tech]

Additional recommended revision of note, as the generator has been revised to supports_multiple_generations = False the code in the class can be significantly simplified to remove accounting for COHERE_GENERATION_LIMIT as it will no longer apply to an implementation what focuses on usage of ClientV2.

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. If you are still interested in this issue, please respond to keep it open. Thank you!