[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>

requirements-lint.txt

@@ -4,5 +4,6 @@ pre-commit==4.0.1
 # type checking
 mypy==1.11.1
 types-PyYAML
+types-regex
 types-requests
 types-setuptools