Related to #94709.

Proposed Changes

• Removes the Card component from the migration credentials screen.

Why are these changes being made?

• To bring the migration flow UI closer to the onboarding flow UI as per p9Jlb4-ee4-p2#comment-13481.

Testing Instructions

• Proceed through the migration flow.
• On the "How do you want to migrate?" step, choose "Do it for me".
• Verify that there is no border around the form and that the background of the page is all the same color.
• Remove the conditional here to see the error.
• Ensure the error message spacing looks good.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?