[TASK] Show a friendly message for non-admin users on the WorkspaceKind page

### Certification

- [x] I certify I am an Epic Owner for Kubeflow Notebooks 2.0 and expected to create planning-related issues.

### Description

Currently, when a non-admin user navigates to the WorkspaceKind page, they see an error (likely a 403 or failed API response rendered as an error state). Until the dashboard supports conditionally hiding the WorkspaceKind navigation item for non-admins, we should handle this gracefully.

Display a friendly informational message (not an error) such as: "WorkspaceKind management is restricted to administrators. Contact your admin if you need changes to workspace configurations."

This should use an appropriate PatternFly empty state pattern (e.g., EmptyState with a lock or info icon) rather than an error alert.

### Acceptance Criteria

- [ ] Non-admin users see a friendly, non-error message on the WorkspaceKind page
- [ ] No error alerts or broken UI states are shown
- [ ] The page is still navigable (back button, sidebar links work)

Start by locating the WorkspaceKind page and its handling of non-admin API failures. Reproduce the page with a non-admin user and inspect the current error state. Done means the page shows a PatternFly informational or locked empty state, avoids error alerts, and preserves navigation such as the back button and sidebar links.

Written by the indexing model from the issue text.