Yes. Lionfish are bony fishes. NOAA classifies red lionfish (Pterois volitans) and devil firefish (Pterois miles) in class Actinopterygii—the ray-finned fishes—which are the living bony fishes, not cartilaginous fishes such as sharks and rays.
That placement sits in the order Scorpaeniformes and family Scorpaenidae. NOAA also notes that lionfish have cycloid scales, a scale type typical of many bony fishes. So in everyday and scientific usage, lionfish count as bony fish.