Change Differentiable.moved(along:) to move(along:). (#236)

Author: dan-zheng

Sources/TensorFlow/Layers/Recurrent.swift

@@ -88,7 +88,7 @@ public struct SimpleRNNCell<Scalar: TensorFlowFloatingPoint>: RNNCell, VectorPro
     // TODO(TF-507): Revert to `typealias State = Tensor<Scalar>` after
     // SR-10697 is fixed.
     public struct State: Equatable, Differentiable, VectorProtocol, KeyPathIterable {
-        public let value: Tensor<Scalar>
+        public var value: Tensor<Scalar>
         public init(_ value: Tensor<Scalar>) {
             self.value = value
         }

Sources/TensorFlow/Optimizer.swift

@@ -291,7 +291,7 @@ public class RiemannSGD<Model: Layer, Scalar: FloatingPoint>: Optimizer
 
     public func update(_ model: inout Model.AllDifferentiableVariables,
                        along direction: Model.TangentVector) {
-        model = model.moved(along: learningRate * (.zero - direction))
+        model.move(along: learningRate * (.zero - direction))
     }
 }