EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA); Scientific Opinion on the substantiation of a health claim related to a combination of <em>Paullinia cupana</em> Kunth (guarana) and <em>Camellia sinensis</em> (L.) Kuntze (green tea) extracts and reduction of body weight pursuant to Article 13(5) of Regulation (EC) No 1924/2006