fix overflow in doctest for 32bit

Author: orxfun

src/tree.rs

@@ -974,7 +974,7 @@ where
     /// use orx_tree::*;
     ///
     /// let num_children = 4;
-    /// let total_depth = 10;
+    /// let total_depth = 8;
     ///
     /// let mut tree = DynTree::new(0.to_string());
     /// let mut dfs = Traversal.dfs().over_nodes();
@@ -1052,7 +1052,7 @@ where
     /// use orx_tree::*;
     ///
     /// let num_children = 4;
-    /// let total_depth = 10;
+    /// let total_depth = 8;
     ///
     /// let mut tree = DynTree::new(0.to_string());
     /// let mut dfs = Traversal.dfs().over_nodes();