linear_solver: Enable multithread in integer programming example

ortools/linear_solver/samples/integer_programming_example.cc

@@ -71,6 +71,7 @@ void IntegerProgrammingExample() {
   // [END objective]
 
   // [START solve]
+  solver->SetNumThreads(8);
   const MPSolver::ResultStatus result_status = solver->Solve();
   // Check that the problem has an optimal solution.
   if (result_status != MPSolver::OPTIMAL) {

ortools/linear_solver/samples/integer_programming_example.py

@@ -64,6 +64,7 @@ def IntegerProgrammingExample():
 
     # Solve the problem and print the solution.
     # [START print_solution]
+    solver.SetNumThreads(8)
     solver.Solve()
     # Print the objective value of the solution.
     print('Maximum objective function value = %d' % solver.Objective().Value())