fix: wrong z order of render buffer blitter

Disable DepthAwareRendering to ensure the uniform render order as
element order.

Author: 18202781743

src/private/dbackdropnode.cpp

@@ -668,10 +668,13 @@ class Q_DECL_HIDDEN RhiNode : public DBackdropNode {
     }
 
     RenderingFlags flags() const override {
+        // FIXME: shoule we support DepthAwareRendering?
+        // When enable DepthAwareRendering, render buffer node may have a wrong order.
+        // Disable DepthAwareRendering here.
         if (Q_UNLIKELY(!contentNode))
-            return BoundedRectRendering | DepthAwareRendering;
+            return BoundedRectRendering;
 
-        return DepthAwareRendering;
+        return {};
     }
 
     void releaseResources() override {