Update recipe_list document to list Natalia recipe 16

Author: sadielbartholomew

docs/source/recipes/recipe_list.txt

@@ -27,4 +27,6 @@ plot_13_recipe.html#sphx-glr-recipes-plot-13-recipe-py
 plot_14_recipe.html#sphx-glr-recipes-plot-14-recipe-py
 <div class="sphx-glr-thumbcontainer subspace collapse contourmap" tooltip="Subspace, Collapse, Contourmap">
 plot_15_recipe.html#sphx-glr-recipes-plot-15-recipe-py
-<div class="sphx-glr-thumbcontainer histogram subspace" tooltip="Histogram, Subspace">
+<div class="sphx-glr-thumbcontainer histogram subspace" tooltip="Histogram, Subspace">
+plot_16_recipe.html#sphx-glr-recipes-plot-16-recipe-py
+<div class="sphx-glr-thumbcontainer histogram subspace" tooltip="Contourmap, Subspace">