GSV: Fix the extra spacing at the bottom

[arthur791004]

Related to https://github.com/Automattic/dotcom-forge/issues/6786, https://github.com/Automattic/dotcom-forge/issues/6788

Proposed Changes

• Fix the extra spacing at the bottom of the fly-out panel

Before	After

Testing Instructions

• Go to /sites?flags=layout/dotcom-nav-redesign-v2
• Open GSV
• Make sure the extra padding is gone

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)?

[matticbot]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-105662

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-105662&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-105662&env=a8c-for-agencies

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[fushar]

Nicee

[candy02058912]

LGTM, but I do wonder what the initial height restriction was for 🤔