doc: revise CI text in collaborator guide

Minor clarifications to text. For example, this moves the "(green or
yellow)" parenthetical closer to the text to which it applies. (It
applies only to Jenkins CI.)

PR-URL: https://github.com/nodejs/node/pull/37526


Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Beth Griggs <bgriggs@redhat.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>