UI: Only set AA_DontCreateNativeWidgetSiblings on Wayland

It seems this introduced various regressions on X11 (and, potentially, on other
platforms too, but needs confirmation). Let's preserve the old ways on current
platforms, and only use this flag on the new Wayland platform.

UI/obs-app.cpp

@@ -1393,7 +1393,6 @@ bool OBSApp::OBSInit()
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 	setAttribute(Qt::AA_UseHighDpiPixmaps);
 #endif
-	setAttribute(Qt::AA_DontCreateNativeWidgetSiblings);
 
 	qRegisterMetaType<VoidFunc>();
 
@@ -1415,6 +1414,8 @@ bool OBSApp::OBSInit()
 		obs_set_nix_platform_display(
 			native->nativeResourceForIntegration("display"));
 
+		setAttribute(Qt::AA_DontCreateNativeWidgetSiblings);
+
 		blog(LOG_INFO, "Platform: Wayland");
 	}
 #endif