remove obsolete parameter

baumgen.js

@@ -182,8 +182,7 @@ class EllipseCrown extends Crown {
 
 
 class Branch {
-    constructor(data, parentBranch=null) {
-        //this.parentBranch = parentBranch;
+    constructor(data) {
         Object.assign(this, data);
         if(typeof this.forks !== "undefined") {
             for (let fork of this.forks) {