[Test] Remove VLLM_USE_V1 in example and tests (#1733)

V1 is enabled by default, no need to set it by hand now. This PR remove
the useless setting in example and tests

- vLLM version: v0.9.2
- vLLM main:
9ad0a4588b

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

examples/offline_dualbatch_overlap_npu.py

@@ -5,7 +5,6 @@ from vllm import LLM, SamplingParams
 
 # enable dual-batch overlap for vllm ascend
 os.environ["VLLM_ASCEND_ENABLE_DBO"] = "1"
-os.environ["VLLM_USE_V1"] = "1"
 
 # Sample prompts.
 prompts = ["The president of the United States is"] * 41