[macOS] Fix build on old architecture (#3182)

## Description

Currently macOS fails to build on old architecture. This PR fixes that.

## Test plan

Run MacOSExample on paper.

apple/RNGestureHandlerButton.h

@@ -10,21 +10,25 @@
 
 #if TARGET_OS_OSX
 
+#if RCT_NEW_ARCH_ENABLED
+
 #include <react/renderer/core/LayoutMetrics.h>
 
 @protocol RCTComponentViewProtocol;
 
+#endif // RCT_NEW_ARCH_ENABLED
+
 @interface RNGestureHandlerButton : NSControl
 #else
 @interface RNGestureHandlerButton : UIControl
-#endif
+#endif // TARGET_OS_OSX
 /**
  *  Insets used when hit testing inside this view.
  */
 @property (nonatomic, assign) UIEdgeInsets hitTestEdgeInsets;
 @property (nonatomic) BOOL userEnabled;
 
-#if TARGET_OS_OSX
+#if TARGET_OS_OSX && RCT_NEW_ARCH_ENABLED
 - (void)mountChildComponentView:(RNGHUIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index;
 - (void)unmountChildComponentView:(RNGHUIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index;
 - (void)updateLayoutMetrics:(const facebook::react::LayoutMetrics &)layoutMetrics

apple/RNGestureHandlerButton.mm

@@ -14,9 +14,13 @@
 #import <React/RCTUIKit.h>
 #endif
 
+#if RCT_NEW_ARCH_ENABLED
+
 #import <React/RCTConversions.h>
 #import <React/RCTFabricComponentsPlugins.h>
 
+#endif
+
 /**
  * Gesture Handler Button components overrides standard mechanism used by RN
  * to determine touch target, which normally would reurn the UIView that is placed
@@ -87,7 +91,7 @@ - (RNGHUIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
 }
 #endif
 
-#if TARGET_OS_OSX
+#if TARGET_OS_OSX && RCT_NEW_ARCH_ENABLED
 - (void)mountChildComponentView:(RNGHUIView *)childComponentView index:(NSInteger)index
 {
   if (childComponentView.superview != nil) {