Yeah, sorry. That was poorly phrased. What I meant to say is that there’s no way for you to terminate the license yourself against NPM’s wishes.
That provision you quoted only takes effect after NPM purges all copies of your code from their systems (including backups). You can’t force them to do that, thus you can’t force them to stop distributing your code. (Though if they willingly choose to eliminate all copies of your code from their systems, then their license ends and they can’t distribute your code anymore unless you grant them a new one.)
So, for example, restoring left-pad from a backup and continuing to distribute it wouldn’t be a problem even if it weren’t already available under an Open Source license.