xla

90a525b5 - Revert PR#3450 and use sparse_gather in gather (#3566)

Revert PR#3450 and use sparse_gather in gather (#3566) * Revert "Fix gather by using xla sparse gather (#3450)" This reverts commit cfb6e690639c4d746a6cc2f245db23d593ba5cbd. * Use sparse_grad option in torch.gather call