Fixed illustration alignment for group milestones promotion

What does this MR do?

Fixes illustration alignment for group milestones promotion

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

No

Why was this MR needed?

#5803 (closed)

Screenshots (if relevant)

Before	After

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug

• Review

  • Has been reviewed by UX
  • Has been reviewed by Frontend

• EE specific content should be in the top level /ee folder

• Conform by the merge request performance guides

• Conform by the style guides

• Squashed related commits together

• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

#5803 (closed)