Update docs on TextInput:style to point to relevant issue

Summary:
Bandaid for #7070. Until this is fixed, the docs should at least be honest the state they're in, so people don't have to go search and wonder.
Closes https://github.com/facebook/react-native/pull/11626

Differential Revision: D4366925

Pulled By: mkonicek

fbshipit-source-id: 082a8a9916ad0f8fbb2955cffbf61142fa2a98a1

Libraries/Components/TextInput/TextInput.js

@@ -476,6 +476,10 @@ const TextInput = React.createClass({
      */
     blurOnSubmit: PropTypes.bool,
     /**
+     * Note that not all Text styles are supported,
+     * see [Issue#7070](https://github.com/facebook/react-native/issues/7070)
+     * for more detail.
+     *
      * [Styles](/react-native/docs/style.html)
      */
     style: Text.propTypes.style,