Update admin Duo UI

What does this MR do and why?

Updates UI of admin Duo settings

• Remove borders
• Use crud-component instead of card
• Use badge for on/off status
• Use default button instead of danger (we already have a confirmation modal using the danger variant)
• Keep description present regardless of on/off status

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Run GDK in SaaS
• Go to Admin Duo settings --> http://gdk.test:3000/admin/gitlab_duo

Links

• ✂️ UX Paper Cuts 18.4 → AI (#548836 - closed)