Summary:
> Explain the **motivation** for making this change. What existing problem does the pull request solve?
The documentation was slightly out of date. Following https://github.com/facebook/react-native/pull/10898, which removed the `platform ios` tag, this updates the inner documentation to remove the reference to iOS.
Closes https://github.com/facebook/react-native/pull/11993
Differential Revision: D4443723
Pulled By: hramos
fbshipit-source-id: b859c9b0fe1f5e564b919663f8c75401a52ffc9f