There is no evidence to suggest that pugs were ever used to take down lions. Pugs are a small breed of dog and would not be capable of hunting or fighting large prey like lions. In fact, the breed was developed primarily as a companion dog and does not have a history of being used for hunting or other working purposes.
It is possible that this confusion came from the pug’s early origins when there were three dog breeds in ancient China that were considered pugs: the lion dog (shih-tzu), the Pekingese, and the lo-sze (pug).