Investigate draft status toggling via commit messages

According to documentation we support toggling draft status based on commit message.

Creating a commit: Add draft:, Draft:, fixup!, or Fixup! to the beginning of a commit message targeting the merge request’s source branch. This is not a toggle, and adding this text again in a later commit doesn’t mark the merge request as ready.

A quick ack isn't showing support for [f]ixup in our current code base.

Investigate where this commit message processing is occurring, and if [f]ixup is still supported. If not, update the documentation