QmlDesigner: fixes property editor

Recent changes in 4.7 rendered the original qml code invalid

Task-number: QTCREATORBUG-2765
Reviewed-by: Marco Bubke

share/qtcreator/qmldesigner/propertyeditor/Qt/ExtendedPane.qml

@@ -7,7 +7,6 @@ QScrollArea {
     horizontalScrollBarPolicy: "Qt::ScrollBarAlwaysOff";
     id: extendedPane;
     visible: false;
-    content: properyEditorExtended;
     QFrame {
         id: properyEditorExtended
         layout: QVBoxLayout {

share/qtcreator/qmldesigner/propertyeditor/Qt/ItemPane.qml

@@ -43,7 +43,6 @@ PropertyFrame {
 
             horizontalScrollBarPolicy: "Qt::ScrollBarAlwaysOff";
             id: standardPane;
-            content: properyEditorStandard;
             QFrame {
                 //minimumHeight: 1100
                 id: properyEditorStandard

share/qtcreator/qmldesigner/propertyeditor/Qt/LayoutPane.qml

@@ -7,7 +7,6 @@ QScrollArea {
     horizontalScrollBarPolicy: "Qt::ScrollBarAlwaysOff";
     id: layoutPane;
     visible: false;
-    content: properyEditorLayout;
     QFrame {
         id: properyEditorLayout;
         layout: QVBoxLayout {