doc: add Retry CI in collaborator guide

PR-URL: #44130
Reviewed-By: Feng Yu <F3n67u@outlook.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>

doc/contributing/collaborator-guide.md

@@ -253,6 +253,10 @@ current job but re-run everything else. Start a fresh CI if more than seven days
 have elapsed since the original failing CI as the compiled binaries for the
 Windows and ARM platforms are only kept for seven days.
 
+If new commits are pushed to the pull request branch after the latest Jenkins
+CI run, a fresh CI run is required. It can be started by pressing "Retry" on
+the left sidebar, or by adding the `request-ci` label to the pull request.
+
 #### Useful Jenkins CI jobs
 
 * [`node-test-pull-request`](https://ci.nodejs.org/job/node-test-pull-request/)