Fix a comment in binary_search_tree code

codes/typescript/chapter_tree/binary_search_tree.ts

@@ -71,7 +71,7 @@ function insert(num: number): void {
             cur = cur.left as TreeNode; // 插入位置在 cur 的左子树中
         }
     }
-    // 插入节点 val
+    // 插入节点
     let node = new TreeNode(num);
     if (pre!.val < num) {
         pre!.right = node;