System information

• AutoDist version: v0.6.0

• Are you willing to contribute it (Yes/No):

Describe the new feature and the current behavior/state
Currently we support TensorFlow <= 2.2.0. Want to support the official TF 2.3.0. Might need to fix some minor bug and change the supported versions here: https://github.com/petuum/autodist/blob/master/autodist/__init__.py#L35 and fix a few bugs if existed.

Will this change the current API? How?

Describe alternatives you've considered

Additional context