Fixed HDRenderPipeline SkyExport to use Blit w/ scale API (so that the output texture is not upside down)

Assets/ScriptableRenderPipeline/HDRenderPipeline/Sky/SkyManager.cs

 
             // Flip texture.
             // Temporarily disabled until proper API reaches trunk
-            //Graphics.Blit(temp, tempRT, new Vector2(1.0f, -1.0f), new Vector2(0.0f, 0.0f));
-            Graphics.Blit(temp, tempRT);
-
+            Graphics.Blit(temp, tempRT, new Vector2(1.0f, -1.0f), new Vector2(0.0f, 0.0f));
+            
             result.ReadPixels(new Rect(0, 0, resolution * 6, resolution), 0, 0);
             result.Apply();