Fix a memory leak in suitesparse.cc

Change-Id: I6eb8b33d927840d6c3631679de482038d9f3673a

internal/ceres/suitesparse.cc

diff --git a/internal/ceres/suitesparse.cc b/internal/ceres/suitesparse.cc
index 024996c..5e93d2e 100644
--- a/internal/ceres/suitesparse.cc
+++ b/internal/ceres/suitesparse.cc
@@ -406,6 +406,7 @@
   }
 
   memcpy(solution, cholmod_dense_solution->x, num_cols * sizeof(*solution));
+  ss_.Free(cholmod_dense_solution);
   return LINEAR_SOLVER_SUCCESS;
 }