[CI] Remove VLLM_TEST_CLEAN_GPU_MEMORY to avoid environment variable pollution that causes unnecessary GPU detection, thereby slowing down test case execution. (#3446)

Signed-off-by: wangyu <410167048@qq.com>
Signed-off-by: [Your Name] <your.email@example.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

docs/contributing/ci/tests_style.md

@@ -213,7 +213,6 @@ E2E Online tests for Qwen3-Omni model with mix input and audio+text output.
 import os
 
 os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
-os.environ["VLLM_TEST_CLEAN_GPU_MEMORY"] = "0"
 
 import threading
 from pathlib import Path