RN: Fix $FlowFixMe in AppContainer
RN: Fix $FlowFixMe in AppContainer

Summary: Fixes the `$FlowFixMe` type errors in `AppContainer`.

Reviewed By: TheSavior

Differential Revision: D7987552

fbshipit-source-id: 5eba319aa2661c2d6d8ed24affc066504096b72c

hoangpham95/react-native,exponent/react-native,javache/react-native,janicduplessis/react-native,exponentjs/react-native,javache/react-native,facebook/react-native,arthuralee/react-native,hoangpham95/react-native,exponentjs/react-native,arthuralee/react-native,janicduplessis/react-native,myntra/react-native,exponent/react-native,hammerandchisel/react-native,pandiaraj44/react-native,pandiaraj44/react-native,hammerandchisel/react-native,facebook/react-native,janicduplessis/react-native,janicduplessis/react-native,javache/react-native,janicduplessis/react-native,exponent/react-native,exponent/react-native,facebook/react-native,facebook/react-native,arthuralee/react-native,pandiaraj44/react-native,janicduplessis/react-native,exponentjs/react-native,javache/react-native,janicduplessis/react-native,hammerandchisel/react-native,arthuralee/react-native,facebook/react-native,pandiaraj44/react-native,hoangpham95/react-native,arthuralee/react-native,javache/react-native,facebook/react-native,myntra/react-native,exponentjs/react-native,pandiaraj44/react-native,hammerandchisel/react-native,pandiaraj44/react-native,hoangpham95/react-native,exponent/react-native,myntra/react-native,hammerandchisel/react-native,javache/react-native,javache/react-native,exponentjs/react-native,pandiaraj44/react-native,hoangpham95/react-native,hammerandchisel/react-native,exponentjs/react-native,myntra/react-native,hammerandchisel/react-native,hoangpham95/react-native,exponentjs/react-native,pandiaraj44/react-native,myntra/react-native,exponent/react-native,facebook/react-native,facebook/react-native,exponent/react-native,javache/react-native,janicduplessis/react-native,hammerandchisel/react-native,hoangpham95/react-native,hoangpham95/react-native,myntra/react-native,myntra/react-native,facebook/react-native,myntra/react-native,exponent/react-native,exponentjs/react-native,myntra/react-native,javache/react-native