[ONNX] Enable tests for opset 12 (#37846)
Summary:
Update ORT nightly version and enable opset 12 tests.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37846
Reviewed By: hl475
Differential Revision: D21467903
Pulled By: houseroad
fbshipit-source-id: 20d249790edfb0091a02ebfc58c3d306087e8471
