Add a missing include

Change-Id: Ide00da72d493c6ce38f4ba6542f7c673d7091bfd

internal/ceres/manifold_test.cc

diff --git a/internal/ceres/manifold_test.cc b/internal/ceres/manifold_test.cc
index 46cd700..e57eaa1 100644
--- a/internal/ceres/manifold_test.cc
+++ b/internal/ceres/manifold_test.cc
@@ -33,6 +33,7 @@
 #include <cmath>
 #include <limits>
 #include <memory>
+#include <utility>
 
 #include "Eigen/Geometry"
 #include "ceres/dynamic_numeric_diff_cost_function.h"