Get rid of v_size and z_size as z_size runs less than 16 were wrong.
Get rid of v_size and z_size as z_size runs less than 16 were wrong.

PiperOrigin-RevId: 190278544

vthorsteinsson/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor