fix broken test vllm:test_kernels - test_attention_selector.py::test_flash_attn (#17873)

Co-authored-by: Stephen Chen <tracelog@meta.com>

tests/kernels/attention/test_attention_selector.py

@@ -188,8 +188,9 @@ def test_flash_attn(monkeypatch: pytest.MonkeyPatch):
         m.setenv(STR_BACKEND_ENV_VAR, STR_FLASH_ATTN_VAL)
 
         # Unsupported CUDA arch
-        monkeypatch.setattr(torch.cuda, "get_device_capability", lambda:
-                            (7, 5))
+        monkeypatch.setattr(torch.cuda,
+                            "get_device_capability",
+                            lambda _=None: (7, 5))
         backend = get_attn_backend(16, torch.float16, None, 16, False)
         assert backend.get_name() != STR_FLASH_ATTN_VAL