I don't recall installing the extension either, so maybe it's an extension installed out of the box like Nuget is, but it's still an extension. If you go to the extension manager it's clearly listed as an installed extension, and does have an uninstall button just asking for you to fix your problem here.
Right, now I see what you mean. I thought the update it was trying to download -was- the extension. That's why I didn't want it. Uninstalling now, thanks for the heads up!
Edit: wait, no, there's a snag. It has an install button, but it's unclickable. And the extension manager says I have to uninstall the extension via Programs and Features... but it's not in there. So it looks like some sort of mandatory extension I don't want but have to keep updated.