[V0 Deprecation] Remove VLLM_USE_V1 from tests (#26341)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/v1/metrics/test_ray_metrics.py

@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-import os
 
 import pytest
 import ray
@@ -10,15 +9,6 @@ from vllm.sampling_params import SamplingParams
 from vllm.v1.engine.async_llm import AsyncEngineArgs, AsyncLLM
 from vllm.v1.metrics.ray_wrappers import RayPrometheusMetric, RayPrometheusStatLogger
 
-
-@pytest.fixture(scope="function", autouse=True)
-def use_v1_only(monkeypatch):
-    """
-    The change relies on V1 APIs, so set VLLM_USE_V1=1.
-    """
-    monkeypatch.setenv("VLLM_USE_V1", "1")
-
-
 MODELS = [
     "distilbert/distilgpt2",
 ]
@@ -39,10 +29,6 @@ def test_engine_log_metrics_ray(
     @ray.remote(num_gpus=1)
     class EngineTestActor:
         async def run(self):
-            # Set environment variable inside the Ray actor since environment
-            # variables from pytest fixtures don't propagate to Ray actors
-            os.environ["VLLM_USE_V1"] = "1"
-
             engine_args = AsyncEngineArgs(
                 model=model, dtype=dtype, disable_log_stats=False, enforce_eager=True
             )