message: [docs] Update explicit latest_checkpoint with `path` returned while saving for object-based checkpointing.
diff: @@ -590,14 +590,14 @@ checkpoint = tfe.Checkpoint(x=x, y=y)
  # Assign new values to the variables and save.
  x.assign(2.)
  -checkpoint.save('/tmp/ckpt')
  +save_path = checkpoint.save('/tmp/ckpt')
  # Change the variable after saving.
  x.assign(11.)
  assert 16. == (x + y).numpy() # 11 + 5
  # Restore the values in the checkpoint.
  -checkpoint.restore('/tmp/ckpt-1')
  +checkpoint.restore(save_path) # save_path='/tmp/ckpt-1'
  assert 7. == (x + y).numpy() # 2 + 5
  ```
  