[fabric] Fix missing import

Summary: See title

Test Plan: Build RNTester

Reviewers: shawndempsey, chpurrer, #rn-desktop

Reviewed By: shawndempsey

Differential Revision: https://phabricator.intern.facebook.com/D49924996

packages/react-native/React/Fabric/Mounting/ComponentViews/LegacyViewManagerInterop/RCTLegacyViewManagerInteropComponentView.mm

@@ -16,6 +16,10 @@
 #import <react/utils/ManagedObjectWrapper.h>
 #import "RCTLegacyViewManagerInteropCoordinatorAdapter.h"
 
+#if TARGET_OS_OSX // [macOS
+#import <React/RCTView.h>
+#endif // macOS]
+
 using namespace facebook::react;
 
 static NSString *const kRCTLegacyInteropChildComponentKey = @"childComponentView";