doc: update security release onboarding

This change is helpful when publishing release announcements.

PR-URL: nodejs#42333
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/contributing/security-steward-on-off-boarding.md

@@ -6,6 +6,7 @@
   to the project and not to use/disclose to their employer.
 * Add them to the security-stewards team in the GitHub nodejs-private
   organization.
+* Add them to the [public website team](https://github.com/orgs/nodejs/teams/website).
 * Ensure they have 2FA enabled in H1.
 * Add them to the standard team in H1 using this
   [page](https://hackerone.com/nodejs/team_members).
@@ -16,6 +17,7 @@
 
 * Remove them from security-stewards team in the GitHub nodejs-private
   organization.
+* Remove them from public website team
 * Unless they have access for another reason, remove them from the
   standard team in H1 using this
   [page](https://hackerone.com/nodejs/team_members).