Don't pass in token_type_ids to BART for GLUE

[ethanjperez]

What does this PR do?

Without this fix, training a BARTForSequenceClassification model with run_pl_glue.py gives TypeError: forward() got an unexpected keyword argument 'token_type_ids', because BART does not have token_type_ids. I've solved this issue in the same way as it's solved for the "distilbert" model, and I can train BART models on SNLI without errors now.

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Who can review?

@patrickvonplaten

[patrickvonplaten]

Thanks for the fix @ethanjperez ! Looks good to me!