Fix UIDevice support enabled for watch on Xcode 26 (#8783)

Author: eriklamanna

Realm/RLMApp.mm

@@ -21,8 +21,10 @@
 #import <sys/utsname.h>
 #if __has_include(<UIKit/UIDevice.h>)
 #import <UIKit/UIDevice.h>
+#ifndef TARGET_OS_WATCH
 #define REALM_UIDEVICE_AVAILABLE
 #endif
+#endif
 
 #import "RLMAnalytics.hpp"
 #import "RLMBSON_Private.hpp"