transformers

8d79e5ca - Fix head masking for TFT5 (#9877)

Fix head masking for TFT5 (#9877) * Fix head_mask and decoder_head_mask in TFT5 models * Enable test_headmasking both fot TFT5 tester and TFT5EncoderOnly tester Co-authored-by: patrickvonplaten <patrick.v.platen@gmail.com>