Use `^` version for react-native preset
Use `^` version for react-native preset

Summary:See https://github.com/facebook/react-native/issues/6798
Closes https://github.com/facebook/react-native/pull/6814

Differential Revision: D3138776

fb-gh-sync-id: f43404e7bfdf0e3e7c6df16681653d1dd4016e1a
fbshipit-source-id: f43404e7bfdf0e3e7c6df16681653d1dd4016e1a

Tredsite/react-native,Tredsite/react-native,Tredsite/react-native,Tredsite/react-native,Tredsite/react-native,Tredsite/react-native,Tredsite/react-native,Tredsite/react-native