fix: remove usage of flash_attn_v3_available

Author: windreamer

tests/test_lmdeploy/test_mtp_guided_decoding.py

@@ -41,7 +41,7 @@
     PytorchEngineConfig,
     SpeculativeConfig,
 )
-from lmdeploy.pytorch.configurations.utils import flash_attn_v3_available
+from lmdeploy.pytorch.backends.cuda.attention import use_fa3
 
 # ---------------------------------------------------------------------------
 # Configuration
@@ -89,7 +89,7 @@ def _make_engine_config():
 # Speculative decoding (ar_spec) requires FlashAttention-3 for the decode
 # kernel; without it the engine will fail at runtime.
 pytestmark = pytest.mark.skipif(
-    not (torch.cuda.is_available() and flash_attn_v3_available()),
+    not (torch.cuda.is_available() and use_fa3),
     reason='GPU + FlashAttention-3 required for MTP + guided decoding integration tests',
 )