Fix build issues of the Unity player

Assets/ScriptableRenderLoop/HDRenderPipeline/SceneSettings/SubsurfaceScatteringParameters.cs

 using System;
-using UnityEditor;
+#if UNITY_EDITOR
+    using UnityEditor;
+#endif
 
 namespace UnityEngine.Experimental.Rendering.HDPipeline
 {
         }
     }
 
+#if UNITY_EDITOR
     [CustomEditor(typeof(SubsurfaceScatteringParameters))]
     public class SubsurfaceScatteringParametersEditor : Editor
     {
             m_Profiles = serializedObject.FindProperty("m_Profiles");
         }
     }
+#endif
 }