Update additives.txt
Update additives.txt

Adding Japanese translation of E551 as found on product 4515996927270
openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server