QmlDesigner.PropertyEditor: Show border between buttons

without this it is not 100% clear that we have separated buttons.

Change-Id: I2d8ee228a0104d68e381d23c5435a1b9cb7cf4cb
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

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

@@ -65,7 +65,6 @@ Item {
         anchors.fill: parent
         RoundedPanel {
             roundLeft: isFirst() && buttonRowButton.roundLeftButton
-            roundRight: isLast()
 
             anchors.fill: parent
             visible: checked
@@ -74,7 +73,6 @@ Item {
 
         RoundedPanel {
             roundLeft: isFirst()
-            roundRight: isLast()
 
             anchors.fill: parent
             visible: !checked

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

@@ -30,8 +30,8 @@ import QtQuick.Layouts 1.0
 Rectangle {
     id: panel
 
-    property bool roundLeft: false
-    property bool roundRight: false
+    property bool roundLeft: true
+    property bool roundRight: true
 
 
     /*