Closes #101110

Proposed Changes

This PR reduces the offset on the top for the sticky plan type selector on mobile to ensure that there is no gap on the top:

Image 1	Image 2

Testing Instructions

• Pull the changes from this branch or navigate to Calypso Live Link
• Navigate to /setup/onboarding/plans?source=sites-dashboard&ref=new-site-popover
• Switch to mobile you in your browser
• Select a paid domain
• Once you are on the plans page, scroll to the bottom and select Compare plans
• Observe that the plan comparison grid is sticky to the top when you scroll

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 UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• 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)?