onnxruntime

Enable optimize_by_onnxruntime call for float32 unet model (#17483)

This makes it possible to call `optimize_by_onnxruntime` for float32 unet if `--use_external_data_format` is also used.

### Motivation and Context
When using `optimize_pipeline.py` without `--float16`, `optimize_by_onnxruntime` was not called for unet.