現金離れって英語でなんて言うの？

I wonder if you have the answer. "Cashless" means a state in which we have less cash or do not have as much cash as we need. In this case, the former meaning is applicable. You should not take trouble to put redundant explanation to "cashless" or to think of any different ways. For instance, you could say, "Digital currency has heralded a cashless society." or "Thanks to digital currency, the world is becoming cashless."