doc: shorten pull request wait time to 48 hours

Currently, we have a 72 rule for how many hours a pull request should
be left open at a minimum. Reduce that time to 48 hours.

PR-URL: nodejs#23082
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>

Author: Trott

doc/onboarding.md

@@ -215,8 +215,8 @@ needs to be pointed out separately during the onboarding.
   labels.
 * Run CI on the PR. Because the PR does not affect any code, use the
   `node-test-pull-request-lite-pipeline` CI task.
-* After two Collaborator approvals for the change and two Collaborator approvals
-  for fast-tracking, land the PR.
+* After one or two approvals, land the PR (PRs of this type do not need to wait
+  for 48 hours to land).
   * Be sure to add the `PR-URL: <full-pr-url>` and appropriate `Reviewed-By:`
     metadata.
   * [`node-core-utils`][] automates the generation of metadata and the landing