Summary:
Currently `TextInput.autoCapitalize` is defaulting to 'none' on Android. This PR sets the default to 'sentences', to match iOS and the PropTypes documentation.
Fixes#14846
Closes https://github.com/facebook/react-native/pull/14853
Differential Revision: D5918196
Pulled By: shergin
fbshipit-source-id: d0d00e75d44a410c6821b4ff8910099aae2b2c7c