doc: specify fast-tracking

Currently the documentation is not specific how fast-tracking should
be applied. This specifies exactly how things should be done to prevent
confusion.

PR-URL: #22929
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: George Adams <george.adams@uk.ibm.com>

COLLABORATOR_GUIDE.md

@@ -183,9 +183,12 @@ can be fast-tracked and may be landed after a shorter delay. For example:
  * Regressions that happen right before a release, or reported soon after.
 
 When a pull request is deemed suitable to be fast-tracked, label it with
-`fast-track`. The pull request can be landed once 2 or more Collaborators
-approve both the pull request and the fast-tracking request, and the necessary
-CI testing is done.
+`fast-track` and add a comment that collaborators may upvote. Please mention the
+collaborators that gave an approval before in that comment. If someone disagrees
+with the fast-tracking request, remove the label and leave a comment why it
+should not be fast-tracked. The pull request can be landed once 2 or more
+Collaborators approve both the pull request and the fast-tracking request, and
+the necessary CI testing is done.
 
 ### Testing and CI