Version updates for tf2_image_retraining.ipynb: - Use %tensorflow_version 2.x instead of manual pip installing. - Switch default runtime to Python 3. - The Python 3 runtime has tensorflow_hub>=0.6.0 by default,   which fixes issue https://github.com/tensorflow/hub/issues/356
Version updates for tf2_image_retraining.ipynb:
- Use %tensorflow_version 2.x instead of manual pip installing.
- Switch default runtime to Python 3.
- The Python 3 runtime has tensorflow_hub>=0.6.0 by default,
  which fixes issue https://github.com/tensorflow/hub/issues/356

PiperOrigin-RevId: 268231671

tensorflow/hub,tensorflow/hub