The read-only user was also removed with a "force password change" requirement.
This applies to all firmware versions from 09.1.00.

Updating from previous versions to 09.1.xx does not remove the read-only user but loading the factory settings from 09.1.xx does. 

The JAVA web interface does not distinguish whether a read-only user exists or not and always shows the option of changing the password for the read-only user in the password dialog. A change in the web interface dialog is no longer planned for Classic Switches in this regard.

However, a read-only user can also be created manually in the CLI to avoid the error message. 

(Hirschmann Railswitch) (Config)#users name user

(Hirschmann Railswitch) (Config)#users passwd user

Enter old password:

Enter new password:******

Confirm new password:******

Password Changed!

(Hirschmann Railswitch) (Config)#