doc: fix common typo involving one-time listeners

Our docs use both "one time listener" and "one-time listener". The
second is more correct. Standardize on that.

PR-URL: https://github.com/nodejs/node/pull/17502


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>