tools: use GitHub Squash and Merge feature when using CQ

PR-URL: https://github.com/nodejs/node/pull/40666
Refs: https://docs.github.com/en/rest/reference/pulls#merge-a-pull-request


Reviewed-By: Mary Marchini <oss@mmarchini.me>
Reviewed-By: Michaël Zasso <targos@protonmail.com>