[ONNX] Upgrade ORT to fix CI (#2579)

* Upgrade ORT to fix build

* Update .travis.yml

.travis.yml

@@ -34,7 +34,7 @@ before_install:
   - |
     if [[ $TRAVIS_PYTHON_VERSION == 3.6 ]]; then
       pip install -q --user typing-extensions==3.6.6
-      pip install -q --user -i https://test.pypi.org/simple/ ort-nightly==1.3.0.dev202005123
+      pip install -q --user -i https://test.pypi.org/simple/ ort-nightly==1.4.0.dev202008122
     fi
   - conda install av -c conda-forge