fix: DownloadAdmin.test.jsx 미사용 waitFor import 제거 (ESLint)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/admin/DownloadAdmin.test.jsx

@@ -1,5 +1,5 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
-import { render, screen, fireEvent, waitFor } from '@testing-library/react';
+import { render, screen, fireEvent } from '@testing-library/react';
 import DownloadAdmin from './DownloadAdmin';
 
 // Mock APIs