Click on it, click remove. I'm not 100% if I had to specifically install it from the add ons menu, but I believe I had to. Also this is Firefox Preview we're

Click on it, click remove. I'm not 100% if I had to specifically install it from the add ons menu, but I believe I had to. Also this is Firefox Preview we're talking about - even if it wasn't able to be uninstalled it's software that's in testing!