Fix some gofmt warnings (#8743)

Signed-off-by: Zou Yu <zouy.fnst@cn.fujitsu.com>

storage/remote/metadata_watcher_test.go

@@ -137,8 +137,8 @@ func TestWatchScrapeManager_ReadyForCollection(t *testing.T) {
 
 	manager := &fakeManager{
 		activeTargets: map[string][]*scrape.Target{
-			"job": []*scrape.Target{target},
-			"dup": []*scrape.Target{targetWithDup},
+			"job": {target},
+			"dup": {targetWithDup},
 		},
 	}
 

storage/remote/queue_manager_test.go

@@ -128,7 +128,7 @@ func TestMetadataDelivery(t *testing.T) {
 	defer m.Stop()
 
 	m.AppendMetadata(context.Background(), []scrape.MetricMetadata{
-		scrape.MetricMetadata{
+		{
 			Metric: "prometheus_remote_storage_sent_metadata_bytes_total",
 			Type:   textparse.MetricTypeCounter,
 			Help:   "a nice help text",