Investigate commit_id handling in DraftsController & API
In https://gitlab.com/gitlab-org/gitlab/-/blob/352f6d27474b04966192c44b5b1e63e844a52b59/app/controllers/projects/merge_requests/drafts_controller.rb we are `tap`ping to cast `params[commit_id]` to `nil` when the incoming value is `undefined`. This was originally add 4+ years ago, and can potentially be removed from `DraftsController` as well as the Draft Notes API
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