Summary:
This PR converts `ProgressViewIOS` from a `createReactClass` component to a functional component, and removes the remaining proptypes. Its use of `NativeMethodsMixin` has been ported to a `forwardRef` to the native component.
Pull Request resolved: https://github.com/facebook/react-native/pull/21588
Reviewed By: hramos
Differential Revision: D10338888
Pulled By: RSNara
fbshipit-source-id: c49807e97a0e2cf774971d9aa5a8426f15a3e48d