Resolve ""Revert this merge request" modal has confusing string"

What does this MR do?

Are there points in the code the reviewer needs to double check?

Changes the text in the Revert merge request modal: Start a new merge request with these changes => Start a new merge request with the revert changes.

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #39917 (closed)