Fix toggle control defaults

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Controls/ToggleControl.cs

             Action changedToggle = () => { OnChangeToggle(); };
             m_Toggle = new UnityEngine.Experimental.UIElements.Toggle(changedToggle);
             m_Toggle.SetEnabled(value.isEnabled);
+            m_Toggle.on = value.isOn;
             panel.Add(m_Toggle);
             Add(panel);
         }