Related to https://github.com/Automattic/automattic-for-agencies-dev/issues/299

Proposed Changes

• This PR adjusts the margin for the site dashboard table. Our previous margin setting did not account for the pagination's bottom bar.

Testing Instructions

For the below testing steps, make sure to run yarn start-a8c-for-agencies locally and then visit http://agencies.localhost:3000/sites.

• To test, add a sufficient number of sites to trigger pagination while simultaneously filling the entire window.
• Verify that the last site is not being cut off.

Before

After

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• https://wpcalypso.wordpress.com/devdocs/docs/testing/index.md 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)?