Fix styling for `app/assets/stylesheets/pages/status.scss`

What does this MR do?

No visual changes. This removes 2 unused CSS selectors. This will rename success_with_warnings to success-with-warnings and failed_with_warnings to failed-with-warnings instances in FE and BE.

What are the relevant issue numbers?

Fix #59929 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer