test: reuse replication compatibility fixtures

Signed-off-by: Feng Ruohang <rh@vonng.com>

cmd/replication-mrf-observability_test.go

@@ -79,7 +79,7 @@ func TestReplicationMRFDropsVisible(t *testing.T) {
 	seen = make(map[string]bool)
 	for _, family := range families {
 		for name, value := range want {
-			if family.GetName() != "minio_replication_"+name {
+			if family.GetName() != replicationCollectorPath.metricPrefix()+"_"+name {
 				continue
 			}
 			seen[name] = true