change default initializer in lstm to uniform_unit_scaling
change default initializer in lstm to uniform_unit_scaling

PiperOrigin-RevId: 167888817

tensorflow/tensor2tensor,waterblue13/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,rsepassi/tensor2tensor,vthorsteinsson/tensor2tensor,vthorsteinsson/tensor2tensor,vthorsteinsson/tensor2tensor,waterblue13/tensor2tensor,rsepassi/tensor2tensor,rsepassi/tensor2tensor,waterblue13/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor,rsepassi/tensor2tensor