examples : disable cb_eval callback for --save-logits (#21553)

examples : disable cb_eval callback for --save-logits (#21553)

This commit updates the debug example to not create the
base_callback_data.

The motivation for this is when using `--save-logits`, which is used by
examples/model-conversion scripts, we often don't care about the tensor
outputs and they just add noise to the output. This changes is quiet by
default we can always remove --save-logits to get the tensor outputs
when debugging.