Update add chef admin

howto/manage-chef.md

@@ -24,9 +24,8 @@ Firstname 'Surname With Spaces' gitlab_email $(openssl rand -hex 20)\
 This is done locally by another chef admin:
-* run `knife actor map` to update the user list
-* run `knife group add actor admins _username_` to add the user
-* run `knife group show admins` to check that the user is in the admin group
+* Run `knife group add user <username> admins`.
+* Run `knife group show admins` to check that the user is in the admin group.
 ## Rotate chef key