[Attention] Remove imports from vllm/attention/__init__.py (#29342)

Signed-off-by: Matthew Bonanni <mbonanni@redhat.com>

vllm/model_executor/models/qwen3.py

@@ -30,7 +30,8 @@ import torch
 from torch import nn
 from transformers import Qwen3Config
 
-from vllm.attention import Attention, AttentionType
+from vllm.attention.backends.abstract import AttentionType
+from vllm.attention.layer import Attention
 from vllm.compilation.decorators import support_torch_compile
 from vllm.config import CacheConfig, VllmConfig
 from vllm.distributed import get_pp_group, get_tensor_model_parallel_world_size