Unbreak levenberg_marquardt_strategy_test

Add a missing quotation mark.

Change-Id: I9d7d3c3d6bd5ac616e0dc23f75845178294c45a6

internal/ceres/levenberg_marquardt_strategy_test.cc

diff --git a/internal/ceres/levenberg_marquardt_strategy_test.cc b/internal/ceres/levenberg_marquardt_strategy_test.cc
index 763cebf..4be742c 100644
--- a/internal/ceres/levenberg_marquardt_strategy_test.cc
+++ b/internal/ceres/levenberg_marquardt_strategy_test.cc
@@ -37,7 +37,7 @@
 #include "ceres/trust_region_strategy.h"
 #include "glog/logging.h"
 #include "gmock/gmock.h"
-#include "gtest/gtest.h
+#include "gtest/gtest.h"
 
 using testing::_;
 using testing::AllOf;