China internally is much more of a free market now, so I’m not sure how they could just disable horns anymore, although you still can’t get away with driving an outside register vehicle inside a city for very long without getting a crackdown by the police (meaning, they can enforce inspection requirements fairly easily).
I’m not sure if it was really Chongqing or some other obscure city like Dalian, I’m going by hearsay 20+ years ago. More recently, Shanghai banned honking in most circumstances in 2007 (inside its outer ring), but it’s enforced with just fines.