Update IsChildOf graph walk in LayersGraph.cs

It looks like the recursion here was intended to use the visited set of nodes as part of its traversal. In a quick test, I saw a Lottie json file load time go from 2 minutes down to 15 seconds.

Author: getrou

source/LottieData/Optimization/LayersGraph.cs

@@ -66,7 +66,7 @@ private bool IsChildOf(GraphNode node, HashSet<GraphNode> visited)
 
                 foreach (var parent in Parents)
                 {
-                    if (parent.Equals(node) || parent.IsChildOf(node))
+                    if (parent.Equals(node) || parent.IsChildOf(node, visited))
                     {
                         return true;
                     }