Brave payments: Line should always appear when user scroll down

[jkup]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Fix #3888

Auditors @bsclifton @bradleyrichter

Test Plan:

Is this an idiomatic react approach for this? Also @bsclifton had a good point about it not being immediately obvious the table scrolls but I'm not sure how best to fix it. The only idea I had was to put focus on the table but that will mess with accessibility if people try to tab around.

Anyone have a good idea how to signal to the user that the table is scrollable?

[bridiver]

@jkup when I run this branch the preferences tab is completely blank. I checked on master and it loads fine

[bridiver]

seems ok after a rebase