'hide sites with <1% usage' should be default on in about:preferences#payments

[mrose17]

Fixes #7520

• 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:

• bring up a brand new browser with no state
• go to about:preferences#payments
• click on 'Advanced Settings'
• verify that 'Hide sites with less than 1% usage' is enabled

[diracdeltas]

lgtm with a proper commit message.

in the future, please assign an issue to yourself when you start working on it. i had assigned #7520 to myself and already made a patch for it too.

[mrose17]

oops! i thought i was getting it... sorry!