Fix an error in the tutorial code for NumericDiffCostFunction

Thanks to Gohteu Nuetah for pointing it out.

Change-Id: Ibfeb9ab9dfbdb259f35b1b8f6b85d30a363db7d4

docs/source/nnls_tutorial.rst

diff --git a/docs/source/nnls_tutorial.rst b/docs/source/nnls_tutorial.rst
index 2bb7584..9c4e585 100644
--- a/docs/source/nnls_tutorial.rst
+++ b/docs/source/nnls_tutorial.rst
@@ -210,8 +210,8 @@
 .. code-block:: c++
 
   CostFunction* cost_function =
-    new NumericDiffCostFunction<NumericDiffCostFunctor, ceres::CENTRAL, 1, 1, 1>(
-        new NumericDiffCostFunctor)
+    new NumericDiffCostFunction<NumericDiffCostFunctor, ceres::CENTRAL, 1, 1>(
+        new NumericDiffCostFunctor);
   problem.AddResidualBlock(cost_function, NULL, &x);
 
 Notice the parallel from when we were using automatic differentiation