Resolve "Clean up padding with Markdown headers"

What does this MR do?

Cleans up spacing for markdown content

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

Spacing across site in places that uses markdown, including issues, mrs, wiki, readme, etc.

Screenshots (if relevant)

Before:

After:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• 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 it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #27827 (closed)