doc: revise Waiting for Approvals documentation

Revise the Waiting for Approvals section of the Collaborator Guide. Keep
sentences short and clear. Split long paragraphs into shorter
paragraphs.

PR-URL: https://github.com/nodejs/node/pull/24845


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>