Yes!
This is labeled as being under CC-BY 4.0. That means you can use it in any work, for free, provided you (A) give credit to the person who made it, and (B) make sure that people who get the dog from you can exercise the same rights to use the dog freely (so your game can be paid, but if someone wants to take the dog out of your /images/ folder and use it on its own they totally can).
(There's a little more legalese which you can see in the linked license but that's the broad strokes).