[BugFix]Fix group list type of mc2. (#3890)

### What this PR does / why we need it?
Fix the precision issue caused by the inconsistency between the group
list type used by mc2 and that of eplb.

---------

Signed-off-by: offline0806 <3337230449@qq.com>

tests/e2e/singlecard/spec_decode_v1/test_v1_mtp_correctness.py

@@ -1,8 +1,5 @@
 from __future__ import annotations
 
-import os
-from unittest.mock import patch
-
 import pytest
 from vllm import SamplingParams
 from vllm.config import CompilationConfig, CUDAGraphMode