Remove obsolete tag support test from DragDropUpload

The tag functionality was removed in the previous commit, so
this test that expected a 'tag' field in the upload FormData
is no longer valid.

frontend/src/components/DragDropUpload.test.tsx

@@ -504,42 +504,4 @@ describe('DragDropUpload', () => {
       });
     });
   });
-
-  describe('Tag Support', () => {
-    it('includes tag in upload request', async () => {
-      let capturedFormData: FormData | null = null;
-      
-      class MockXHR {
-        status = 200;
-        responseText = JSON.stringify({ artifact_id: 'abc123', size: 100 });
-        timeout = 0;
-        upload = { addEventListener: vi.fn() };
-        addEventListener = vi.fn((event: string, handler: () => void) => {
-          if (event === 'load') setTimeout(handler, 10);
-        });
-        open = vi.fn();
-        send = vi.fn((data: FormData) => {
-          capturedFormData = data;
-        });
-      }
-      vi.stubGlobal('XMLHttpRequest', MockXHR);
-      
-      render(<DragDropUpload {...defaultProps} />);
-      
-      const input = document.querySelector('input[type="file"]') as HTMLInputElement;
-      const file = createMockFile('test.txt', 100, 'text/plain');
-      
-      Object.defineProperty(input, 'files', {
-        value: Object.assign([file], { item: (i: number) => [file][i] }),
-      });
-      
-      fireEvent.change(input);
-      
-      await vi.advanceTimersByTimeAsync(100);
-      
-      await waitFor(() => {
-        expect(capturedFormData?.get('tag')).toBe('v1.0.0');
-      });
-    });
-  });
 });