Fix internal types on top of TextInput refactor

Summary:
Types were moved out of TextInput into TextInputTypes for better re-use. Fixing the internal callsites.

This isn't much of a worry externally because these types aren't exposed as part of the public API

Reviewed By: RSNara

Differential Revision: D10517066

fbshipit-source-id: bade4285eafb3d7ab5ab1e4b0730c22d45925509

Libraries/Components/TextInput/TextInput.js

@@ -161,7 +161,7 @@ class TextInput extends React.Component<Props> {
   };
 
   _inputRef: ?React.ElementRef<Class<TextInputType>> = null;
-  _lastNativeText: ?string = null;
+  _lastNativeText: ?Stringish = null;
   _lastNativeSelection: ?Selection = null;
   _rafId: ?AnimationFrameID = null;