[ui] FilterComboBox: fix issue clicking on last menu item

Disable the horizontal scrollbar in the popup menu that was
interfering with mouse click selection on the last item.
Also, remove the unneeded Layout policy on the root ColumLayout
of this popup's contentItem.

meshroom/ui/qml/Controls/FilterComboBox.qml

@@ -74,7 +74,6 @@ ComboBox {
 
     popup.contentItem: ColumnLayout {
         width: parent.width
-        Layout.maximumHeight: root.Window.height
         spacing: 0
 
         RowLayout {
@@ -120,6 +119,8 @@ ComboBox {
         ScrollView {
             Layout.fillWidth: true
             Layout.fillHeight: true
+            ScrollBar.horizontal.policy: ScrollBar.AlwaysOff
+
             ListView {
                 implicitHeight: contentHeight
                 clip: true