[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>

tests/e2e/multicard/test_pipeline_parallel.py

@@ -16,7 +16,7 @@
 #
 import pytest
 
-from tests.conftest import VllmRunner
+from tests.e2e.conftest import VllmRunner
 
 MODELS = [
     "Qwen/Qwen3-0.6B",