Resolve "Performance MR widget is expandable even when there are no changes"

What does this MR do?

• Hide Expand button when there are no Perf changes
• show tick instead of warning

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
• EE specific content should be in the top level /ee folder
• Conforms to the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered

What are the relevant issue numbers?

Closes #6766 (closed)