How to enable the :screenshot command from Firefox Web Console

Firefox’s :screenshot command claims that you can do this:

Once you’re in the Web Console, you can type :sc and then hit Tab to autocomplete :screenshot.

On my version of Firefox, 61.0.1, running on Ubuntu 18.04, It shows this when I attempt it Ctrl+Shiftt+k I see:

I do see the icon in the upper right corner, so then why isn't the command working? Did they remove it?