chore(server): remove useless client allowGuestDemoWorkspace config (#12988)

#### PR Dependency Tree


* **PR #12988** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
* Removed the configuration option that allowed guests to access demo
workspaces. This affects related settings in the system configuration
and admin interface.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.docker/selfhost/schema.json

@@ -597,11 +597,6 @@
           "type": "string",
           "description": "Allowed version range of the app that allowed to access the server. Requires 'client/versionControl.enabled' to be true to take effect.\n@default \">=0.20.0\"",
           "default": ">=0.20.0"
-        },
-        "allowGuestDemoWorkspace": {
-          "type": "boolean",
-          "description": "Allow guests to access demo workspace.\n@default true",
-          "default": true
         }
       }
     },