Given the bad quality of the other French translation for “foil packs inside for freshness”,
I would assume right away that it’s just a translation mistake.

Nothing in French is both plural and singular in a way that would justify using both “aux” and “à” at the same time, it’s just not a thing.
So definitely a translation mistake.
the right translation would be : “Thé à la cardamome”

(also “Des emballages aluminium à l’intérieur pour plus de fraîcheur” would be way better for the other one)