monitoring: run go fmt

monitoring/monitoring_on.go

@@ -8,7 +8,7 @@ import (
 
 	"google.golang.org/grpc"
 
-	"github.com/grpc-ecosystem/go-grpc-prometheus"
+	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
 	"github.com/lightningnetwork/lnd/lncfg"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )