Add documentation about diff versions limit
What does this MR do and why?
- Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/517497+
- Related to Add a upper limit for merge request diffs versions (!183063 - merged)
- Related to [Feature flag] Rollout of `merge_requests_diffs... (#521970 - closed)
References
Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.
Edited by Amy Qualls