Revert "Run test_fx_to_onnx_with_onnxruntime serially (#100298)"
This reverts commit 3a3f781f6cd90abbceb63a9cb59546d892ef899e.
Reverted https://github.com/pytorch/pytorch/pull/100298 on behalf of https://github.com/huydhn due to No need as https://github.com/pytorch/pytorch/pull/100297 has been landed ([comment](https://github.com/pytorch/pytorch/pull/100298#issuecomment-1528476786))
