replace onnx producer_version when updating results (#41910)
Summary:
xref gh-39002 which handled the reading but not the writing of the onnx expect files, and the last comment in that PR which points out `XXX` was suboptimal.
xref [this comment](https://github.com/pytorch/pytorch/pull/37091#discussion_r456460168) which pointed out the problem.
This PR:
- replaces `XXX` with `CURRENT_VERSION` in the stored files
- ensures that updating the results with the `--accept` flag will maintain the change
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41910
Reviewed By: pbelevich
Differential Revision: D22758671
Pulled By: ezyang
fbshipit-source-id: 47c345c66740edfc8f0fb9ff358047a41e19b554
