Fix a typo in postprocessing.jl

Author: amontoison

src/postprocessing.jl

@@ -13,7 +13,7 @@ function postprocess!(
     color_used = zeros(Bool, nb_colors)
 
     # nonzero diagonal coefficients force the use of their respective color (there can be no neutral colors if the diagonal is fully nonzero)
-    if !augmented_system(g)
+    if !augmented_graph(g)
         for i in axes(S, 1)
             if !iszero(S[i, i])
                 color_used[color[i]] = true