The `TokenRatesController` was accidentally broken in #8744, when the
logic for starting and stopping polling was moved from the `isActive`
property to start/stop functions.
A reference to the now-obsolete `isActive` property was accidentally
left behind, resulting in no exchange rate updates.
* Use @metamask/eslint-config@1.1.0
* Use eslint-plugin-mocha@6.2.2
* Mark root ESLint config as root
* Update Mocha ESLint rules with shared ESLint config