iOS: 6/7 JS only. Remove logic for visible prop in JS, and pass it to native

Summary: Changelog: [Fabric][iOS] Use non-global event emitter for onDismiss event for <Modal>

Reviewed By: fkgozali

Differential Revision: D28138741

fbshipit-source-id: df9069e523f2e8bd1b85f3d9be55cfd300f89d66

Libraries/Modal/Modal.js

@@ -219,7 +219,7 @@ class Modal extends React.Component<Props> {
   }
 
   render(): React.Node {
-    if (this.props.visible !== true) {
+    if (Platform.OS !== 'ios' && this.props.visible !== true) {
       return null;
     }