doc: edit for concision

This removes some wordy phrases (notably "it is important to note
that").

PR-URL: https://github.com/nodejs/node/pull/17891


Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>