remove completed TODO (#479)

Co-authored-by: guyinyou <guyinyou.gyy@alibaba-inc.com>
diff --git a/golang/client_manager.go b/golang/client_manager.go
index 38be735..99655af 100644
--- a/golang/client_manager.go
+++ b/golang/client_manager.go
@@ -29,7 +29,6 @@
 	"google.golang.org/grpc/status"
 )
 
-// TODO: no global clientManager
 type ClientManager interface {
 	RegisterClient(client Client)
 	UnRegisterClient(client Client)