That’s just their news notification via matray, it automatically grabs anything from the Manjaro forum RSS feed or their twitter account. I don’t think it’s unreasonable for this to have been on twitter or their forum, and don’t count it as an ad in your desktop. If you don’t like it popping up (and don’t care about not getting other updates in your tray from their RSS or twitter) just delete matray
Matrimony sounds like macaroni - i.e. macaroni and cheese