[BigBird Pegasus] Make tests faster (#11744)
[BigBird Pegasus] Make tests faster (#11744)

* improve tests

* remove bogus file

* make style

Co-authored-by: Patrick von Platen <cbb7353e6d953ef360baf960c122346276c6e320@huggingface.co>
huggingface/transformers,huggingface/transformers,huggingface/pytorch-transformers,huggingface/transformers,huggingface/transformers