Remove deprecated assertEquals (#6532)
Remove deprecated assertEquals (#6532)

`assertEquals` is deprecated: https://stackoverflow.com/questions/930995/assertequals-vs-assertequal-in-python/931011
This PR replaces these deprecated methods.
huggingface/transformers,huggingface/pytorch-transformers,huggingface/transformers,huggingface/transformers,huggingface/transformers