Remove V0 attn fusion test

Signed-off-by: Luka Govedič <lgovedic@redhat.com>

Author: ProExpertProg

tests/compile/test_fusion_attn.py

@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 import copy
-from typing import Optional
 
 import pytest
 import torch._dynamo
@@ -39,10 +38,6 @@
 FP8_DTYPE = current_platform.fp8_dtype()
 FP4_DTYPE = torch.uint8
 
-# globals needed for string-import custom Dynamo backend field
-backend: Optional[TestBackend] = None
-backend_unfused: Optional[TestBackend] = None
-
 
 class AttentionQuantPatternModel(torch.nn.Module):
     """Base model for AttentionQuantPattern fusion."""