Make Payments FAQ link obvious

[cndouglas]

Test plan

1. With a new session, launch Brave, open preferences, and go to Payments
2. The FAQ link should be orange (per screenshot below) and very obviously be a link
3. Click link, confirm it goes to FAQ

Description

Fixes #7487

• 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).

Test Plan: See issue #7487 for QA steps.

Screenshot:

[bsclifton]

Looks great, thanks! 😄