In ledger notifications offer option to "Don't notify me anymore"

[ayumi]

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

Describe the issue you encountered:
We have a preference for Ledger notifications, but it's unclear that exists when you actually view a notification.
For example, when getting the "Add more funds.." the default behavior is to wait a while then show the message again.

Expected behavior:
On ledger notifications, offer a clear way to disable ledger notifications (dismiss notifications forever).

• Brave Version:
  0.12.7

• Any related issues:
  Aggressive notification #4481 / Aggressive notifications

@bradleyrichter @bsclifton