Fix bug in the `xformer_translate` model when `pack_examples=True` from the dataset `translate_wmt`.
Fix bug in the `xformer_translate` model when `pack_examples=True` from the dataset `translate_wmt`.

`inputs_positions` should be `inputs_position` and `targets_positions` should be `targets_position`.

PiperOrigin-RevId: 484547483

google/init2winit