Unauthenticated sources warning in Chrome

When in the Control Panel I’m seeing a warning in Google Chrome that the page is trying to load scripts from an unauthenticated source. The file it doesn’t like is http://ping.ellislab.com/core-message.js Which is obviously due to the http rather than https, but I can’t find that address in any file in the install so I can fix it. I think it is hidden in themes/javascript/compressed/cp/global_end.js which adds the nag message about it not being a registered install, but Core doesn’t need to be registered. EE version = Core v2.11.6

I realize that this isn’t important, and it’s just Google trying to be good, but my clients don’t understand that and think that EE isn’t safe to use. So I’m looking for a quick fix, as I will need to apply this to several sites.