Disable swipe down gesture in Modal component

Summary:
Changelog: [internal]

Paper implementation prevents swipe to dismiss gesture in Modal.

https://www.internalfb.com/intern/diffusion/FBS/browse/master/xplat/js/react-native-github/React/Views/RCTModalHostViewController.m?commit=9d1f344633fb&lines=25-30

This diff implements the same in Fabric.

Reviewed By: ShikaSD

Differential Revision: D26910753

fbshipit-source-id: cb036ce0a9cd57c7d549a1a58eb941d8e64f2468

React/Fabric/Mounting/ComponentViews/Modal/RCTFabricModalHostViewController.mm

@@ -22,6 +22,13 @@
   }
   _touchHandler = [RCTSurfaceTouchHandler new];
 
+#if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && defined(__IPHONE_13_0) && \
+    __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_13_0
+  if (@available(iOS 13.0, *)) {
+    self.modalInPresentation = YES;
+  }
+#endif
+
   return self;
 }