FYI, anytime there's a new version of a plugin, there's a delay before it shows up on the official list of plugins that calibre watches. (It's managed manually by kiwidude and Kovid.)
But you don't have to wait for it. You can go into your User Plugins, view your Installed plugins, choose FanFictionDownLoader and, even though it says there's no new version, click 'Install'. Restart calibre and you'll have the latest version.