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I was reading up on how to control the selected value of a `SegmentedControlIOS` component and noticed that the prop was written wrong in the description.
1. This PR changes only the content of a component description comment, and not any code.
Closes https://github.com/facebook/react-native/pull/15742
Differential Revision: D5757116
Pulled By: hramos
fbshipit-source-id: faccb95fb3a4ba2852c457c3559c066da09e6bb9
3834cb5f68