Fix iOS Paper Scroll Event RTL check (#40751)

Summary:
Pull Request resolved: #40751

In D48379915 I fixed inverted `contentOffset` in `onScroll` events on iOS. I thought I tested on Paper, but I think this was during a period where the Paper route in Catalyst was actually launching Fabric (oops).

In Paper, at least under `forceRTL` and English, `[UIApplication sharedApplication].userInterfaceLayoutDirection` is not set to RTL. We instead have a per-view `reactLayoutDirection` we should be reading.

This sort of thing isn't currently set on Fabric, which checks application-level RTL. This seems... not right with being able to set `direction` in a subtree context, but Android does the same thing, and that would take some greater changes.

Changelog:
[iOS][Fixed] - Fix iOS Paper Scroll Event RTL check

Reviewed By: luluwu2032

Differential Revision: D50098310

fbshipit-source-id: e321fca7b2f7983e903e23237bc2d604c72f98a3

packages/react-native/React/Views/ScrollView/RCTScrollView.m

@@ -1058,7 +1058,7 @@ - (void)sendScrollEventWithName:(NSString *)eventName
   }
 
   CGPoint offset = scrollView.contentOffset;
-  if ([UIApplication sharedApplication].userInterfaceLayoutDirection == UIUserInterfaceLayoutDirectionRightToLeft) {
+  if ([self reactLayoutDirection] == UIUserInterfaceLayoutDirectionRightToLeft) {
     offset.x = scrollView.contentSize.width - scrollView.frame.size.width - offset.x;
   }