LpNormNormalizingTransformer does not support exporting to Onnx

- **What did you do?**
Created a pipeline from NormalizeLpNorm and tried to export it to Onnx with ConvertToOnnxProtobuf. 

- **What happened?**
The transform wasn't saved in the onnx graph

- **What did you expect?**
The transform should be saved in the onnx graph
