Fix the button distance on the milestone page

What does this MR do and why?

The button distance in the group > milestone was not correct. In this MR, I tried to fix it at the right distance.

Screenshots or screen recordings

As-is	To-be

How to set up and validate locally

• Review App: https://gitlab-review-fix-button-kh2m2s.gitlab-review.app/groups/gitlab-qa-sandbox-group/-/milestones
• GDK
  • Navigate to any groups in the GDK
  • Find the Issues > Milestones

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.