Helper text for MangoHud doesn't tell you the proper command

So if you click the warning sign you get a message to run this:

`flatpak install --user org.freedesktop.Platform.VulkanLayer.MangoHud`

However, if you try running this, you get the following error:

`error: No remote refs found for ‘org.freedesktop.Platform.VulkanLayer.MangoHud’`

What you need is to also add the add-remote option and potentially the --if-not-exists flag.