doc: improve the instructions of onboarding PR

PR-URL: #18268
Fixes: #18090
Refs: nodejs/TSC#472
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>

doc/onboarding.md

@@ -199,12 +199,13 @@ onboarding session.
 * Optionally, include your personal pronouns.
 * Label your pull request with the `doc` subsystem label.
 * Run CI on your PR.
-* After one or two approvals, land the PR.
+* After one or two approvals, land the PR (PRs of this type do not need to wait
+  for 48/72 hours to land).
   * Be sure to add the `PR-URL: <full-pr-url>` and appropriate `Reviewed-By:`
-    metadata!
-  * [`core-validate-commit`][] helps a lot with this – install and use it if you
-    can!
-  * [`node-core-utils`][] fetches the metadata for you.
+    metadata.
+  * [`core-validate-commit`][] automates the validation of commit messages.
+  * [`node-core-utils`][] automates the generation of metadata and the landing
+    process. See the documentation of [`git-node`][].
 
 ## Final notes
 
@@ -227,6 +228,7 @@ onboarding session.
 
 [Code of Conduct]: https://github.com/nodejs/admin/blob/master/CODE_OF_CONDUCT.md
 [`core-validate-commit`]: https://github.com/evanlucas/core-validate-commit
+[`git-node`]: https://github.com/nodejs/node-core-utils#git-node
 [`node-core-utils`]: https://github.com/nodejs/node-core-utils
 [Landing Pull Requests]: https://github.com/nodejs/node/blob/master/COLLABORATOR_GUIDE.md#landing-pull-requests
 [https://github.com/nodejs/node/commit/ce986de829457c39257cd205067602e765768fb0]: https://github.com/nodejs/node/commit/ce986de829457c39257cd205067602e765768fb0