[Test] Cleanup for helpers (#6523)

Signed-off-by: wangyu <410167048@qq.com>
Signed-off-by: [Your Name] <your.email@example.com>
Co-authored-by: amy-why-3459 <wuhaiyan17@huawei.com>

tests/diffusion/distributed/test_tensor_parallel.py

@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
 
 """DiT tensor-parallel parity and perf checks for diffusion models.
 
@@ -18,8 +18,8 @@ import pytest
 import torch
 from PIL import Image
 
-from tests.helpers.env import DeviceMemoryMonitor
 from tests.helpers.mark import hardware_test
+from tests.helpers.monitor import DeviceMemoryMonitor
 from tests.helpers.runtime import OmniRunner
 from vllm_omni.diffusion.data import DiffusionParallelConfig
 from vllm_omni.inputs.data import OmniDiffusionSamplingParams