Summary:
I inserted an 'in' in the warning message that is displayed when the user's package.json file doesn't have a valid version number for react native.
Test plan
---------------
-run upgrade.js on a project with an invalid version number.
Closes https://github.com/facebook/react-native/pull/7314
Differential Revision: D3245839
fb-gh-sync-id: e38f3be0884d8c75f9610faced85d5c81c24a49e
fbshipit-source-id: e38f3be0884d8c75f9610faced85d5c81c24a49e