fix: binary tree image error

[xgqfrms]

fix: binary tree image error

https://coffe1891.gitbook.io/frontend-hard-mode-interview/2/2.1.4

solution

https://github.com/coffe1891/frontend-hard-mode-interview/blob/master/2/2.1.4.md

- ![](http://img.blog.csdn.net/20150204101904649?%3C/p%3E%3Cp%3Ewatermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvTXlfSm9icw==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center)

+ ![image](https://user-images.githubusercontent.com/7291672/152813666-575ead67-af69-46a6-8cba-dc12060cabb5.png)