Fix build sidebar build details padding

What does this MR do?

Removes a .block-first overriding declaration that was added to fix the coverage padding and moved the padding that fixes the coverage block to a .block.coverage declaration.

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

Why was this MR needed?

The build sidebar build details had too much padding as seen in #22529 (closed).

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #22529 (closed)