set tab size

What does this MR do?

change tab size of views of search and diffs

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

Browser compatible.

Why was this MR needed?

in the views of search and diffs, tab width is too wide, and in most IDEs, its width is always 4, not 8.

Screenshots (if relevant)

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?