doc: update 2fa information in onboarding.md

Because it is no longer possible to add someone to the nodejs GitHub
organization if they do not have two-factor authentication enabled,
update the text of the onboarding documentatino to reflect this.

PR-URL: nodejs#18968
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Matheus Marchini <matheus@sthima.com>

doc/onboarding.md

@@ -5,20 +5,17 @@ onboarding session.
 
 ## One week before the onboarding session
 
-* Confirm that the new Collaborator is using two-factor authentication on their
-  GitHub account. Unless two-factor authentication is enabled, do not give an
-  account elevated privileges such as the ability to land code in the main
-  repository or to start continuous integration (CI) jobs.
+* If the new Collaborator is not yet a member of the nodejs GitHub organization,
+  confirm that they are using two-factor authentication. It will not be possible
+  to add them to the organization if they are not using two-factor
+  authentication.
 * Announce the accepted nomination in a TSC meeting and in the TSC
   mailing list.
 
 ## Fifteen minutes before the onboarding session
 
 * Prior to the onboarding session, add the new Collaborator to
   [the Collaborators team](https://github.com/orgs/nodejs/teams/collaborators).
-  Note that this is the step that gives the account elevated privileges, so do
-  not perform this step (or any subsequent steps) unless two-factor
-  authentication is enabled on the new Collaborator's GitHub account.
 
 ## Onboarding session