Yes, it's confusing but just install the new Lightroom release. In the Creative Cloud app Lightroom always shows as an install not as an update.
Whenever Lightroom is shown as an install in the creative cloud manager, that is an indication that there is an update available. There is a Lightroom 5.7.1 update that has been released. But there isn't really an update process for Lightroom other than to install the newer version. The 5.7.1 update had some bug fixes and support changes for a Sony camera, I believe.
Thanks to Jim and Wolf. I was worried that by re-installing Lightroom, it would wipe out any customization that I have made, but that has not seemed to happen. Why does Lightroom not show that I need to do an update when I am in the application and "check for Updates?"