fix go vet error in proxy example (#1377)

Author: marten-seemann

examples/http-proxy/proxy.go

@@ -234,8 +234,7 @@ Usage: Start remote peer first with:   ./proxy
 
 Then you can do something like: curl -x "localhost:9900" "http://ipfs.io".
 This proxies sends the request through the local peer, which proxies it to
-the remote peer, which makes it and sends the response back.
-`
+the remote peer, which makes it and sends the response back.`
 
 func main() {
 	flag.Usage = func() {