Remove LogBox.ignoreWarnings
Remove LogBox.ignoreWarnings

Summary:
This method isn't necessary for the migration to LogBox because we have a YellowBoxDeprecated module instructing users to use LogBox.ignoreLogs (so no old code should be calling LogBox.ignoreWarnings).

Changelog: [Internal]

Reviewed By: motiz88

Differential Revision: D19950302

fbshipit-source-id: 4850884e770f812273978b9a205f5b914e5a9d2f

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