Mention when the Registry API was introduced

What does this MR do?

Builds upon https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24303 and adds when the feature was introduced.

Related issues

https://gitlab.com/gitlab-org/gitlab-ce/issues/55978

Author's checklist

• Apply the correct labels and milestone

Review checklist

• Technical writer's review (required)
• Merge after https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24303 is merged