GraphicBuffer.h: Remove redundant friend class declaration causing warnings

Change-Id: I8a4b0e0b4d0a1cf472de820553c31f2d42044543
diff --git a/include/ui/GraphicBuffer.h b/include/ui/GraphicBuffer.h
index d3839ea..4b9b5a8 100644
--- a/include/ui/GraphicBuffer.h
+++ b/include/ui/GraphicBuffer.h
@@ -124,7 +124,6 @@
     friend class Surface;
     friend class BpSurface;
     friend class BnSurface;
-    friend class Surface;
     friend class LightRefBase<GraphicBuffer>;
     GraphicBuffer(const GraphicBuffer& rhs);
     GraphicBuffer& operator = (const GraphicBuffer& rhs);