How to clear Facebook's image cache

The way to "force" facebook to clear their cache for a specific url is to use the Debugger tool.

I tried using the debugger with the url of the image and it shows the new image and not the old one, though when trying the cached link you posted the old image still appears.

I suspect that if you try to post new posts the new icon will be used and not the old cached version, but that link you posted probably won't be changed.