Remove unnecessary scroll bar on shields v2 for details view

[srirambv]

Description

Remove unnecessary scroll bar on shields v2 for details view

Steps to Reproduce

1. Enable Shields v2 flag
2. Visit any site and open shields
3. Expand to advance view and click on blocked items, shows unnecessary scrollbars

Actual result:

Expected result:

Only show scrollbar when there is an overflow from visible box

Reproduces how often:

Easy

Brave version (brave://version info)

With flag enabled

Version/Channel Information:

• Can you reproduce this issue with the current release?
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

cc: @nullhook @aguscruiz

[MadhaviSeelam]

Brave	1.38.71 Chromium: 100.0.4896.46 (Official Build) beta (64-bit)
Revision	5ca33821b2211805855c77d334353d27c616a7ca-refs/branch-heads/4896@{#584}
OS	Windows 11 Version 21H2 (Build 22000.556)

Install 1.38.x
Launch Brave
Enable brave://flags/#brave-shields-v2
Click Relaunch

Testcase 1: No scrollbar displayed if there is no overflow of blocked items

• Visited https://www.euronews.com/news/international
• Open Shields and expand to Advance Controls
• Click on the count (16) for Trackers and ads blocked
• Verified there is no scrollbar displayed that listed blocked items in the box

ex1	ex2

Testcase 2: Scrollbar displayed if there is overflow of blocked items

• Visited another site, youtube.com
• Play a video
• Opened Shields and expand to Advance Controls
• Clicked on the count (40) for Trackers and ads blocked
• Clicked on (+) for one of the items to expand
• Verified scrollbar displayed when there is an overflow from visible box