tests: Enable tst_tabbingWithAffinities for QtQuick

src/private/DropArea_p.h

@@ -25,6 +25,8 @@
 #include "MultiSplitter_p.h"
 #include "DropIndicatorOverlayInterface_p.h"
 
+class TestCommon;
+
 namespace KDDockWidgets {
 
 class Frame;
@@ -64,6 +66,7 @@ private:
     Q_DISABLE_COPY(DropArea)
     friend class Frame;
     friend class TestDocks;
+    friend class ::TestCommon;
     friend class DropIndicatorOverlayInterface;
     friend class AnimatedIndicators;
     friend class FloatingWindow;