[applet] Don't show configure button when in system tray

The system tray representation provides the button for us

src/applet/package/contents/ui/Toolbar.qml

@@ -53,7 +53,7 @@ PlasmaExtras.PlasmoidHeading {
         PlasmaComponents3.ToolButton {
             id: openSettingsButton
 
-            visible: plasmoid.action("configure").enabled
+            visible: plasmoid.action("configure").enabled && !(plasmoid.containmentDisplayHints & PlasmaCore.Types.ContainmentDrawsPlasmoidHeading)
             icon.name: "configure"
             onClicked: plasmoid.action("configure").trigger()