ledger balance updater doesn't turn on/off when payments tab is activated

[bridiver]

Test plan

1. Launch Brave and open Preferences > Payments
2. Enable Brave Payments
3. If you'd like to ensure the balance is being fetched properly, restore a wallet (otherwise, you can test knowing it's always $0)
4. Verify the balance is shown
5. Switch tabs (open a tab, go to brave.com for example)
6. Switch back to the Preferences > Payment tab. It should re-fetch the balance
7. Close the Preferences > Payments tab
8. Re-open the Preferences > Payments tab
9. Verify the balance is shown

Original issue description

• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  https://github.com/brave/browser-laptop/blob/master/app/renderer/components/main/main.js#L514
  uses tabs, but tabs has been removed from windowState
  This change also makes the check substantially more efficient

• Platform (Win7, 8, 10? macOS? Linux distro?):
  All

• Brave Version (revision SHA):
  6ec909c

• Is this an issue in the currently released version?

• Can this issue be consistently reproduced?

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:

• Any related issues: