The first answer here did not help me, possibly because they were talking about this button over an image in their "first option," whereas in my case it's just there because of a copy/paste action and no image at all. The second option did apply to me, but there was no Convert option when I Clicked File.

So, I just came up with a hack: just drag this box off to the side, past the edge of the document, and then it's just not visible and no longer annoying.