Doc: Update reference to new `gitlab-qa` binary.
The old bin/qa
binary should now be gitlab-qa
as per
https://gitlab.com/gitlab-org/gitlab-qa/blob/master/docs/run_qa_against_gdk.md
Edited by 🤖 GitLab Bot 🤖
The old bin/qa
binary should now be gitlab-qa
as per
https://gitlab.com/gitlab-org/gitlab-qa/blob/master/docs/run_qa_against_gdk.md