[CI] Fix CI by addressing max_split_size_mb config (#3258)

### What this PR does / why we need it?
Fix CI by addressing max_split_size_mb config

### Does this PR introduce _any_ user-facing change?
No, test onyl

### How was this patch tested?
Full CI passed, espcially eagle one


- vLLM version: v0.10.2
- vLLM main:
https://github.com/vllm-project/vllm/commit/releases/v0.11.0

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

tests/e2e/singlecard/spec_decode_v1/test_v1_mtp_correctness.py

@@ -1,14 +1,10 @@
 from __future__ import annotations
 
-import os
-
 import pytest
 from vllm import SamplingParams
 
 from tests.e2e.conftest import VllmRunner
 
-os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
-
 
 @pytest.fixture
 def sampling_config():

tests/e2e/singlecard/spec_decode_v1/test_v1_mtp_torchair_correctness.py

@@ -1,14 +1,10 @@
 from __future__ import annotations
 
-import os
-
 import pytest
 from vllm import SamplingParams
 
 from tests.e2e.conftest import VllmRunner
 
-os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
-
 
 @pytest.fixture
 def sampling_config():

tests/e2e/singlecard/spec_decode_v1/test_v1_spec_decode.py

@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 from __future__ import annotations
 
-import os
 import random
 from typing import Any
 
@@ -10,9 +9,6 @@ from vllm import LLM, SamplingParams
 
 from tests.e2e.conftest import VllmRunner
 
-os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
-os.environ["PYTORCH_NPU_ALLOC_CONF"] = "max_split_size_mb:256"
-
 
 @pytest.fixture
 def test_prompts():