Back out "iOS: 6/7 JS only. Remove logic for visible prop in JS, and …

…pass it to native"

Summary:
Changelog: [Internal]

back out D28138741 (40706e0)

Differential Revision: D28709374

fbshipit-source-id: c7085588ab4573c0ca18a2324f8e1ed40384753c

Libraries/Modal/Modal.js

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