Remove unnecessary serialized properties

com.unity.shadergraph/Editor/Drawing/Controls/GradientControl.cs

         [SerializeField]
         SerializedObject m_SerializedObject;
 
-        [SerializeField]
-        SerializedProperty m_SerializedProperty;
-
         public GradientControlView(string label, AbstractMaterialNode node, PropertyInfo propertyInfo)
         {
             m_Node = node;
             m_GradientObject = ScriptableObject.CreateInstance<GradientObject>();
             m_GradientObject.gradient = new Gradient();
             m_SerializedObject = new SerializedObject(m_GradientObject);
-            m_SerializedProperty = m_SerializedObject.FindProperty("gradient");
 
             var gradient = (Gradient)m_PropertyInfo.GetValue(m_Node, null);
             m_GradientObject.gradient.SetKeys(gradient.colorKeys, gradient.alphaKeys);

com.unity.shadergraph/Editor/Drawing/Views/Slots/GradientSlotControlView.cs

         [SerializeField]
         SerializedObject m_SerializedObject;
 
-        [SerializeField]
-        SerializedProperty m_SerializedProperty;
-
         public GradientSlotControlView(GradientInputMaterialSlot slot)
         {
             m_Slot = slot;
             m_GradientObject.gradient = new Gradient();
             m_SerializedObject = new SerializedObject(m_GradientObject);
-            m_SerializedProperty = m_SerializedObject.FindProperty("gradient");
             
             m_GradientObject.gradient.SetKeys(m_Slot.value.colorKeys, m_Slot.value.alphaKeys);
             m_GradientObject.gradient.mode = m_Slot.value.mode;