road map loss tracing, just keep use 'Design' describe the 'Future'

Signed-off-by: Smark <smark@freecoop.net>

libnetwork/README.md

@@ -89,9 +89,6 @@ func main() {
 }
 ```
 
-## Future
-Please refer to [roadmap](ROADMAP.md) for more information.
-
 ## Contributing
 
 Want to hack on libnetwork? [Docker's contributions guidelines](https://github.com/docker/docker/blob/master/CONTRIBUTING.md) apply.