Summary:
Fix the following warning:
> Module RCTTVNavigationEventEmitter requires main queue setup since it overrides `init` but doesn't implement `requiresMainQueueSetup`. In a future release React Native will default to initializing all native modules on a background thread unless explicitly opted-out of.
Trivial change.
[IOS] [MINOR] [RCTTVNavigationEventEmitter] - Implement `requiresMainQueueSetup` in `RCTTVNavigationEventEmitter`
Closes https://github.com/facebook/react-native/pull/16915
Differential Revision: D6394636
Pulled By: shergin
fbshipit-source-id: 3981655832715e73e93ef917d987e25097029b84