fix fa4 integration

src/diffusers/models/attention_dispatch.py

@@ -540,7 +540,7 @@ def _check_attention_backend_requirements(backend: AttentionBackendName) -> None
                 f"Backend '{backend.value}' needs to be used with a `kernels` version of at least 0.12. Please update with `pip install -U kernels`."
             )
 
-        if backend == AttentionBackendName.FLASH_4_HUB and not is_kernels_available(">=", "0.12.3"):
+        if backend == AttentionBackendName.FLASH_4_HUB and not is_kernels_version(">=", "0.12.3"):
             raise RuntimeError(
                 f"Backend '{backend.value}' needs to be used with a `kernels` version of at least 0.12.3. Please update with `pip install -U kernels`."
             )