Fix classes attached to recipe 16 filter keywords

Author: sadielbartholomew

docs/source/recipes/recipe_list.txt

@@ -29,4 +29,4 @@ plot_14_recipe.html#sphx-glr-recipes-plot-14-recipe-py
 plot_15_recipe.html#sphx-glr-recipes-plot-15-recipe-py
 <div class="sphx-glr-thumbcontainer histogram subspace" tooltip="Histogram, Subspace, Subplot">
 plot_16_recipe.html#sphx-glr-recipes-plot-16-recipe-py
-<div class="sphx-glr-thumbcontainer histogram subspace" tooltip="Contourmap, Subspace, Subplot">
+<div class="sphx-glr-thumbcontainer contourmap subspace subplot" tooltip="Contourmap, Subspace, Subplot">