[Doctest] `Add configuration_whisper.py`
Add `configuration_whisper.py` to `utils/documentation_tests.txt` for doctest.

Based on issue https://github.com/huggingface/transformers/issues/19487

@sgugger could you please check it?
Thanks :)
@daspartho There is an extra empty line which fails the tests. Could you remove it? Thanks.

In fact, you can use `make style` to see the necessary change(s).<|||||>@ydshieh removed it, should work nicely now :)<|||||>_The documentation is not available anymore as the PR was closed or merged._