Back out "[react-native][PR] Remove the deprecated `isIPhoneX_deprecated` constant"

Summary:
Original commit changeset: 0b0b3a2d7b80

This constant is still in use at Facebook. Its removal has been pushed to sometime in the future.

Reviewed By: mdvacca

Differential Revision: D8721213

fbshipit-source-id: d1197c96804e4d2dc96be27421e5248a2394cdac

RNTester/js/SafeAreaViewExample.js

@@ -90,8 +90,8 @@ exports.examples = [
     title: 'isIPhoneX_deprecated Example',
     description:
       '`DeviceInfo.isIPhoneX_deprecated` returns true only on iPhone X. ' +
-      'Note: This prop is deprecated and will be removed right after June 01, 2018. ' +
-      'Please use this only for a quick and temporary solution. ' +
+      'Note: This prop is deprecated and will be removed in a future ' +
+      'release. Please use this only for a quick and temporary solution. ' +
       'Use <SafeAreaView> instead.',
     render: () => <IsIPhoneXExample />,
   },

React/Modules/RCTDeviceInfo.m

@@ -103,7 +103,7 @@ static NSDictionary *RCTExportedDimensions(RCTBridge *bridge)
   return @{
     @"Dimensions": RCTExportedDimensions(_bridge),
     // Note:
-    // This prop is deprecated and will be removed right after June 01, 2018.
+    // This prop is deprecated and will be removed in a future release.
     // Please use this only for a quick and temporary solution.
     // Use <SafeAreaView> instead.
     @"isIPhoneX_deprecated": @(RCTIsIPhoneX()),