Auth: Fix a wrong command in a comment
Summary: `bin/revoke` does not exist. Make it `bin/auth revoke`.
Test Plan: Try commands on the command line.
Reviewers: O1 Blessed Committers, valerio.bozzolan
Reviewed By: O1 Blessed Committers, valerio.bozzolan
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26273