Update listener port parsing in WAF service

- Modify comment to clarify port extraction from `HostsAndPort` field
- Improve code readability by updating inline documentation

internal/service/waf.go

@@ -605,7 +605,7 @@ func (s *wafService) EnableListenerWafs(ctx context.Context, req *EnableListener
 	desiredPortSet := sets.NewInt()
 	wafMap := map[int][]string{}
 	for _, listener := range req.Listeners {
-		// get port from listener, like hosts1@127.0.0.1@abc.com-8080
+		// get port from listener.HostsAndPort, like hosts1@127.0.0.1@abc.com-8080
 		index := strings.LastIndex(listener.HostsAndPort, "-")
 		if index == -1 {
 			return fmt.Errorf("failed to get listener port: %v", listener)