doc: do not use tilde for "about" or "approximately"

Refs: https://docs.microsoft.com/en-us/style-guide/a-z-word-list-term-collections/term-collections/special-characters

PR-URL: https://github.com/nodejs/node/pull/39344


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Darshan Sen <raisinten@gmail.com>