Just ignore it. We created the extension with the CS6 extension manager, and you get this message in CS5.5.
Adobe dropped support for the extension manager for Dreamweaver CC.. you can use a free third party extension manager instead like:
http://www.projectseven.com/products/ex-man/info.htm
or
https://www.dmxzone.com/go/22670/dmxzone-extension-manager-for-dreamweaver/