Resolve "Modify the empty state of changes in MR"

What does this MR do?

Updates the empty state in MR diff tab

Screenshots

@hazelyang The illustration change needs to be done separately, we need to publish a new version of gitlab-svg

Does this MR meet the acceptance criteria?

• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #41357 (closed)