A federal appeals court on Tuesday revived a dismissed class-action lawsuit against Hill’s Pet Nutrition and PetSmart over a line of expensive cat food branded as prescription-only that is “not materially different” from regular cat food.Holly B. Vanzant and Dana Land are cat owners who bought Hill’s Prescription Diet cat food for their pets.They allege they paid a premium price for the food at PetSmart stores under the impression it was prescription-only, but later learned the food was allegedly …