doc: streamline Accepting Modifications in Collaborator Guide

Editing a sentence I missed simplifying in the last pass on that
section.

PR-URL: https://github.com/nodejs/node/pull/24807


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>