onnx-simplifier简化时强制设置不合并concat
ref: https://github.com/daquexian/onnx-simplifier/issues/94#issuecomment-706077511
run onnxsim with --skip-optimizer fuse_consecutive_concats
example:
python -m onnxsim --skip-optimizer fuse_consecutive_concats your.onnx your_simplified.onnx