[skip ci]Fix golint error for SetRootCoord in QueryCoord (#10806)

Signed-off-by: cai.zhang <cai.zhang@zilliz.com>

internal/distributed/querycoord/service.go

@@ -238,6 +238,7 @@ func (s *Server) Stop() error {
 	return err
 }
 
+// SetRootCoord sets the RootCoord's client for QueryCoord component.
 func (s *Server) SetRootCoord(m types.RootCoord) error {
 	s.queryCoord.SetRootCoord(m)
 	return nil