Replace ModalFullscreenView constants by Dimensions

Reviewed By: jingc

Differential Revision: D2954172

fb-gh-sync-id: 8b2f68d13632de25830678ddc32a36c239970427
shipit-source-id: 8b2f68d13632de25830678ddc32a36c239970427

Author: javache

React/Modules/RCTUIManager.m

@@ -1265,10 +1265,6 @@ static void RCTMeasureLayout(RCTShadowView *view,
         @"height": @(RCTScreenSize().height),
         @"scale": @(RCTScreenScale()),
       },
-      @"modalFullscreenView": @{
-        @"width": @(RCTScreenSize().width),
-        @"height": @(RCTScreenSize().height),
-      },
     },
   }];