[ONNX]Enable tests in test_operators.py (#39431)
Summary:
Enable Dropout and SoftmaxCrossEntropy tests in test_operators.py
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39431
Reviewed By: hl475
Differential Revision: D21877501
Pulled By: houseroad
fbshipit-source-id: 1e9b1e5cf80dc1843bdbde2662f3339e357c6654
