Summary:
Fixed a typo in `ToastAndroid.js`'s comment.
No test plan. Just fix a typo.
Closes https://github.com/facebook/react-native/pull/15802
Differential Revision: D5767578
Pulled By: hramos
fbshipit-source-id: 4ccc708800f7d4259d266fba195981a85e6647a1