Use the MR IID in the docs Review Apps URLs
What does this MR do?
We're taking advantage of the pipelines for merge requests https://docs.gitlab.com/ee/ci/merge_request_pipelines/.
This will result in a nicer URL which will be more informative than the previous one where a string of random characters was used.
This was previously opened in gitlab-foss!24360 (closed), but we hadn't enabled MR pipelines at that time.