Don't hard-code the application name

As a response to the comment on commit d501f7730a42e45177fa3cdb89a4cdce1f1bd9a4.

plugins/Toolbox/resources/qml/components/ToolboxFooter.qml

@@ -42,7 +42,7 @@ Item
             rightMargin: UM.Theme.getSize("wide_margin").width
         }
         height: UM.Theme.getSize("toolbox_footer_button").height
-        text: catalog.i18nc("@info:button", "Quit Ultimaker Cura")
+        text: catalog.i18nc("@info:button, %1 is the application name", "Quit %1").arg(CuraApplication.applicationDisplayName)
         onClicked: toolbox.restart()
     }