QmlJSTools: Fix language detection bug.

Due to what looks like a copy/paste error, qbs files were detected
as actual QML, resulting in a torrent of parser warnings for projects
containing qbs files.

Change-Id: I8f4886621641d42bb0b2aa066a0bbdc44b9d8221
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>