tools/etcd-test-proxy: remove newline in "Fprintln"

Fix govet warnings with Go tip

```
tools/etcd-test-proxy/main.go:47: Fprintln arg list ends with redundant
newline
```

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

tools/etcd-test-proxy/main.go

@@ -62,8 +62,7 @@ $ ./bin/etcd-test-proxy --help
 $ ./bin/etcd-test-proxy --from localhost:23790 --to localhost:2379 --http-port 2378 --verbose
 
 $ ETCDCTL_API=3 ./bin/etcdctl --endpoints localhost:2379 put foo bar
-$ ETCDCTL_API=3 ./bin/etcdctl --endpoints localhost:23790 put foo bar
-`)
+$ ETCDCTL_API=3 ./bin/etcdctl --endpoints localhost:23790 put foo bar`)
 		flag.PrintDefaults()
 	}