Sorry, the answer is actually properly provided here : Input System 1.3.0 released: more fixes (post #15) and it cannot be more clear.
It’s also a good and robust way of implementing the “Wait for any key” through code with events, so you don’t clutter your project needlessly. Even though it’s recommended to segregate functionality (so input should really be in its own manager), this is the perfect exception to the rule : you just need to register that one key press event, wait for it, then de-register it.
Clean and efficient.