[ci] Onnx test 3->2 shards (#97383)
Nit, not entirely sure why onnx needs an extra shard, it also doesn't seem to be doing anything.
https://github.com/pytorch/pytorch/actions/runs/4494513193/jobs/7907327958
The test step is 2 minutes long
Pull Request resolved: https://github.com/pytorch/pytorch/pull/97383
Approved by: https://github.com/huydhn
