Fix translation with an argument

There are multiple issues with that line:
* Other languages might have the application name before their version of 'About'. The previous line can't account for those languages because the application name is always appended at the end.
* The old one was trying to translate CuraApplication.applicationDisplayName which can't be statically determined.
* The old one had no explanation towards the translator.

resources/qml/Dialogs/AboutDialog.qml

@@ -1,4 +1,4 @@
-// Copyright (c) 2018 Ultimaker B.V.
+// Copyright (c) 2020 Ultimaker B.V.
 // Cura is released under the terms of the LGPLv3 or higher.
 
 import QtQuick 2.2
@@ -12,7 +12,7 @@ UM.Dialog
     id: base
 
     //: About dialog title
-    title: catalog.i18nc("@title:window","About " + catalog.i18nc("@title:window", CuraApplication.applicationDisplayName))
+    title: catalog.i18nc("@title:window The argument is the application name.", "About %1").arg(CuraApplication.applicationDisplayName)
 
     minimumWidth: 500 * screenScaleFactor
     minimumHeight: 650 * screenScaleFactor