[skip ci] Add the comments to service (#13507)

Signed-off-by: jingkl <jingjing.jia@zilliz.com>

internal/distributed/proxy/service.go

@@ -373,6 +373,7 @@ func (s *Server) LoadPartitions(ctx context.Context, request *milvuspb.LoadParti
 	return s.proxy.LoadPartitions(ctx, request)
 }
 
+// ReleasePartitions notifies Proxy to release the partitions data
 func (s *Server) ReleasePartitions(ctx context.Context, request *milvuspb.ReleasePartitionsRequest) (*commonpb.Status, error) {
 	return s.proxy.ReleasePartitions(ctx, request)
 }