[Fabric] Fix scroll views hiding content underneath them in Fabric. (microsoft#1820)

* Fix scroll views hiding content underneath them in Fabric.

* Clean up Paper scroll view after shim scroll view fix.

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Co-authored-by: Nick <lefever@meta.com>

Author: lenaic

React/Base/macOS/RCTUIKit.m

@@ -451,6 +451,7 @@ - (instancetype)initWithFrame:(CGRect)frame
 {
   if (self = [super initWithFrame:frame]) {
     self.scrollEnabled = YES;
+    self.drawsBackground = NO;
   }
 
   return self;

React/Views/ScrollView/RCTScrollView.m

@@ -476,7 +476,6 @@ - (instancetype)initWithEventDispatcher:(id<RCTEventDispatcherProtocol>)eventDis
     _scrollView.delegate = self;
     _scrollView.delaysContentTouches = NO;
 #else // [macOS
-    _scrollView.drawsBackground = NO;
     _scrollView.postsBoundsChangedNotifications = YES;
     _lastScrollPosition = NSZeroPoint;
 #endif // macOS]