[JENKINS-73930] Put back the disabled warning

[Dohbedoh]

See JENKINS-73930. Amend

The button was removed from #419. But along with the warning. It is not obvious anymore when a folder is disabled.

Before:

After:

Proposed changelog entries

• Re-instaore the Disabled warning when a Folder is disabled

Submitter checklist

• JIRA issue is well described
• Changelog entry appropriate for the audience affected by the change (users or developer, depending on the change).
  * Use the Internal: prefix if the change has no user-visible impact (API, test frameworks, etc.)
• Appropriate autotests or explanation to why this change has no tests