message: Update debugger.md
  Should be using normal softmax not sparse.
diff: @@ -400,7 +400,7 @@ diff = -(y_ * tf.log(y))
  to the built-in, numerically-stable implementation of softmax cross-entropy:
  ```python
  -diff = tf.losses.sparse_softmax_cross_entropy(labels=y_, logits=logits)
  +diff = tf.losses.softmax_cross_entropy(labels=y_, logits=logits)
  ```
  Rerun with the `--debug` flag as follows:
  