[EE] Reduce differences with CE in a migration spec

What does this MR do?

CE backport at https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26162.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• EE specific content should be in the top level /ee folder
• Security reports checked/validated by reviewer