[bugfix][CI] Diffusers backend update (#3096)

Signed-off-by: Huang, Zeyu <11222265+fhfuih@users.noreply.github.com>
Signed-off-by: Zeyu Huang | 黃澤宇 <11222265+fhfuih@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

tests/diffusion/test_diffusion_scheduler.py

@@ -414,7 +414,7 @@ class TestDiffusionEngine:
 
     def test_dummy_run_raises_on_output_error(self, mocker: MockerFixture) -> None:
         engine = DiffusionEngine.__new__(DiffusionEngine)
-        engine.od_config = SimpleNamespace(model_class_name="mock_model")
+        engine.od_config = SimpleNamespace(model_class_name="mock_model", diffusion_load_format="default")
         engine.pre_process_func = None
         engine.add_req_and_wait_for_response = mocker.Mock(return_value=DiffusionOutput(error="boom"))