message: Fix TensorBoard python -m invoke in docs
diff: @@ -198,7 +198,7 @@ You're now all set to visualize this data using TensorBoard.
  ## Launching TensorBoard
  To run TensorBoard, use the following command (alternatively `python -m
  -tensorflow.tensorboard`)
  +tensorboard.main`)
  ```bash
  tensorboard --logdir=path/to/log-directory
  