Simplify Dot Autodiff (#412)

* Simplify Dot Autodiff

* remove commented code

src/ngraph/ops/dot.cpp

@@ -133,11 +133,9 @@ void op::Dot::generate_adjoints(autodiff::Adjoints& adjoints, const std::shared_
     J_shape.insert(J_shape.begin(), y_shape.begin(), y_shape.begin() + m_reduction_axes_count);
     K_shape.insert(K_shape.begin(), y_shape.begin() + J_shape.size(), y_shape.end());
 
-    auto delta_reshaped = make_reshape_axes_to_front(delta, I_shape, K_shape);       // KI
-    auto delta_reshaped_dot_y = make_shared<Dot>(y, delta_reshaped, K_shape.size()); // JI
-    auto delta_reshaped_dot_y_reshaped =
-        make_reshape_axes_to_front(delta_reshaped_dot_y, J_shape, I_shape); // IJ
-    adjoints.add_delta(x, delta_reshaped_dot_y_reshaped);
+    auto y_reshaped = make_reshape_axes_to_front(y, J_shape, K_shape);               // KI
+    auto delta_dot_y_reshaped = make_shared<Dot>(delta, y_reshaped, K_shape.size()); // JI
+    adjoints.add_delta(x, delta_dot_y_reshaped);
 
     auto x_reshaped = make_reshape_axes_to_front(x, I_shape, J_shape);               // JI
     auto x_reshaped_dot_delta = make_shared<Dot>(x_reshaped, delta, I_shape.size()); // JK