QmlDesigner.PropertyEditor: fix property name in LayoutSection

Change-Id: I3ca4d1930a90c9d84019061f32a8d34d646fce98
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>

share/qtcreator/qmldesigner/propertyEditorQmlSources/QtQuick/LayoutSection.qml

@@ -348,7 +348,7 @@ Section {
         RowLayout {
             anchors.left: parent.left
             anchors.right: parent.right
-            visible: anchorBackend.verticalAnchored;
+            visible: anchorBackend.verticalCentered;
 
             IconLabel {
                 source:  "../HelperWidgets/images/anchor-vertical.png"