ClangTidy fixes part 3

Change-Id: I69587f663b8d91a465ed068a82f9e09e3b7a72e2

internal/ceres/line_search_minimizer_test.cc

diff --git a/internal/ceres/line_search_minimizer_test.cc b/internal/ceres/line_search_minimizer_test.cc
index 1825b36..576d90e 100644
--- a/internal/ceres/line_search_minimizer_test.cc
+++ b/internal/ceres/line_search_minimizer_test.cc
@@ -28,7 +28,6 @@
 //
 // Author: sameeragarwal@google.com (Sameer Agarwal)
 
-#include <cstdlib>
 #include <limits>
 
 #include "ceres/ceres.h"

internal/ceres/sparse_cholesky_test.cc

diff --git a/internal/ceres/sparse_cholesky_test.cc b/internal/ceres/sparse_cholesky_test.cc
index 18a6342..2b8e852 100644
--- a/internal/ceres/sparse_cholesky_test.cc
+++ b/internal/ceres/sparse_cholesky_test.cc
@@ -34,6 +34,7 @@
 #include <memory>
 #include <random>
 #include <sstream>
+#include <string>
 #include <utility>
 #include <vector>