Adds margin between buttons in CI header

What does this MR do?

Backports CSS added for 9.4 to 9.3.

Does this MR meet the acceptance criteria?

• Tests
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #33879 (closed)