[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/quantization/test_gguf_diffusion.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
 """End-to-end tests for GGUF quantization on diffusion models.
 
 Validates that GGUF-quantized diffusion models generate valid images and
@@ -19,8 +19,8 @@ import numpy as np
 import pytest
 import torch
 
-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.inputs.data import OmniDiffusionSamplingParams
 from vllm_omni.outputs import OmniRequestOutput