Current best hparams for local 2d.

def img2img_transformer2d_q3():
  """Current best hparams for local 2d."""
  hparams = img2img_transformer2d_q1()
  hparams.batch_size = 2
  hparams.query_shape = (8, 16)
  hparams.memory_flange = (8, 32)
  return hparams