Plugin seems stuck, can't remove or edit it

I’ve been playing with this plugin and now can’t seem to remove it. It doesn’t show up in my widgets but it does on the website. Also to get any changes with sidebar widgets I have to clear my cache, something I’ve never had to do before. This is the website http://www.muddbunnies.com. Can you let me know how I can remove this plugin?

https://ww.wp.xz.cn/plugins/recent-facebook-posts/