Fix CUDA graph decode capture crash in AITER FlashAttention (#36042)

Signed-off-by: Martin Yuan <myuan@meta.com>
Co-authored-by: Martin Yuan <myuan@meta.com>

vllm/v1/attention/backends/rocm_aiter_fa.py

@@ -1152,11 +1152,10 @@ class AiterFlashAttentionImpl(AttentionImpl):
                 decode_max_query_len = attn_metadata.decode_metadata.max_query_len
 
                 # Use unified_attention for speculative decoding (multi-token)
-                # or when sliding window is enabled
-                if self.sliding_window[0] != -1 or decode_max_query_len > 1:
+                if decode_max_query_len > 1:
                     assert not rocm_aiter_ops.is_shuffle_kv_cache_enabled(), (
-                        "Shuffle KV cache layout is not supported with sliding "
-                        "window or speculative decoding (multi-token decode)."
+                        "Shuffle KV cache layout is not supported with "
+                        "speculative decoding (multi-token decode)."
                     )
                     from aiter.ops.triton.unified_attention import (
                         unified_attention,