Fix camera preview - Remove obsolete code

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/Camera/HDCameraEditor.Handlers.cs

             EditorUtility.CopySerialized(cameraData, m_PreviewAdditionalCameraData);
             var layer = c.GetComponent<PostProcessLayer>() ?? ComponentSingleton<PostProcessLayer>.instance;
             EditorUtility.CopySerialized(layer, m_PreviewPostProcessLayer);
-            m_PreviewCamera.cameraType = CameraType.SceneView; // This is required else if we use Preview the image is flipped... (Unity...)
-
-            // We need to call UpdateDirtyFrameSettings to update the dirty flags that was set in the CopySerialized call
-            m_PreviewAdditionalCameraData.UpdateDirtyFrameSettings(true, cameraData.GetFrameSettings());
-            // And then to copy the runtime frame settings
-            // So this includes the runtime frame settings properly
-            cameraData.GetFrameSettings().CopyTo(m_PreviewAdditionalCameraData.GetFrameSettings());
-            m_PreviewHDCamera.Update(m_PreviewAdditionalCameraData.GetFrameSettings(), m_PreviewPostProcessLayer, null);
+            m_PreviewCamera.cameraType = CameraType.Preview;
 
             var previewTexture = GetPreviewTextureWithSize((int)previewSize.x, (int)previewSize.y);
             m_PreviewCamera.targetTexture = previewTexture;

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/Camera/HDCameraEditor.cs

         Camera m_PreviewCamera;
         HDAdditionalCameraData m_PreviewAdditionalCameraData;
         PostProcessLayer m_PreviewPostProcessLayer;
-        HDCamera m_PreviewHDCamera;
 
         void OnEnable()
         {
             m_PreviewCamera.cameraType = CameraType.Preview; // Must be init before adding HDAdditionalCameraData
             m_PreviewAdditionalCameraData = m_PreviewCamera.gameObject.AddComponent<HDAdditionalCameraData>();
             m_PreviewPostProcessLayer = m_PreviewCamera.gameObject.AddComponent<PostProcessLayer>();
-            m_PreviewHDCamera = new HDCamera(m_PreviewCamera);
-            m_PreviewHDCamera.Update(m_PreviewAdditionalCameraData.GetFrameSettings(), m_PreviewPostProcessLayer, null);
         }
 
         void OnDisable()

ScriptableRenderPipeline/HDRenderPipeline/HDRP/RenderPipeline/FrameSettings.cs

             aggregate.ConfigureMSAADependentSettings();
             aggregate.ConfigureStereoDependentSettings();
 
+            // Note: Camera preview is both the preview of a material and the preview of a camera (Unity doesn't make a distinction here)
             if (camera.cameraType == CameraType.Preview)
             {
                 // remove undesired feature in preview