doc: update Useful CI Jobs section of Collaborator Guide

Revise the Useful CI Jobs section of the Collaborator Guide to be more
clear and concise.

PR-URL: https://github.com/nodejs/node/pull/24916


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>