pin tensorflow 2 nightly version to date 06/08 (#381)
pin tensorflow 2 nightly version to date 06/08 (#381)

* pin tf2 version to 0608

* pin to 06/05

tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs-converter,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs-converter,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs-converter,tensorflow/tfjs,tensorflow/tfjs-converter,tensorflow/tfjs-converter