* Use AutoTokenizer by default, to easily adapt to new models and tokenizers
* Add missing AutoTokenizer import
* Apply Black
* Missing import
* Fix DPR tests
* Remove tests on max length
* Update Documentation & Code Style
Co-authored-by: Sara Zan <sara.zanzottera@deepset.ai>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>