Training: remove tag `static-XXX+cuXXX-model` in exported ONNX model

[trivoldus28]

Can we remove this static-XXX+cuXXX-model tag in the exported ONNX files? Seems unnecessary when the ONNX file format is supposed to be framework agnostic.

Reason for change: I find it hard to programmatically scan checkpoints across models without hardcoding and when the tag changes after an upgrade across models.