Avoid admin_closed message on open forms

Problem/Motivation

When user limit is enabled on a form, the admin_closed message is shown to subscribed users with the permission 'submission_update_any'.

Steps to reproduce

Create a form, with a limit user 1.
Create a submission on the form with a user who has the permission 'sumission_update_any'.
The "This webform is closed. Only submission administrators are allowed to access this webform and create new submissions." message is printed, below the limit_user_message.
At this point, the webform is not closed. This is confusing for these specific users.

Proposed resolution

Remove the WebformMessageManagerInterface::ADMIN_CLOSED message from when checking user limit.