This has been fixed in 5.3.11 which was a hot-fix we released this evening. We are no longer showing this to anyone other than a site admin or, if you're running multi-site, a Network Admin.
If you'd like to disable the Dashboard widget for admin's too, you can do so on the options page by unchecking the option: "Enable activity report widget on dashboard:" and saving the options.
Regards,
Mark.