remove empty assignment as required in code review

admin.go

@@ -558,7 +558,7 @@ func (ca *clusterAdmin) ListConsumerGroups() (allGroups map[string]string, err e
 		wg.Add(1)
 		go func(b *Broker, conf *Config) {
 			defer wg.Done()
-			_ = b.Open(conf) // Ensure that broker is opened
+			b.Open(conf) // Ensure that broker is opened
 
 			response, err := b.ListGroups(&ListGroupsRequest{})
 			if err != nil {