QmlDesigner.PropertyEditor: disabling slider in SliderSpinBox

This just looks broken atm.

Change-Id: Id7064fa92e3bbfeac693cf500ec268090e641ea4
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>

share/qtcreator/qmldesigner/propertyEditorQmlSources/HelperWidgets/SliderSpinBox.qml

@@ -58,6 +58,7 @@ SpinBox {
         minimumValue: spinBox.minimumValue
 
         value: spinBox.value
+        visible: false
 
         onValueChanged: {
             spinBox.value = value

share/qtcreator/qmldesigner/propertyEditorQmlSources/HelperWidgets/SpinBox.qml

@@ -74,7 +74,7 @@ Controls.SpinBox {
         anchors.right: parent.right
         anchors.top: parent.bottom
         height: 10;
-        visible: spinBox.hasSlider
+        visible: false
 
         maximumValue: spinBox.maximumValue
         minimumValue: spinBox.minimumValue