Workhorse: Remove duplicated response body from DWS response

What does this MR do and why?

Currently, the response body is duplicated for actions with HTTP Response. It's done for backward compatibility to support both version while we migrating from one format to another. Now, when chore: set legacy response from new response (gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!3394 - merged) duplicates the message on DWS side, we can remove the duplicated response on the client side to reduce the load.