message: Re-add ILU structure test
diff: using namespace mfem;
  -/*
  TEST_CASE("ILU Structure", "[ILU]")
  {
  int N = 5;
  @@ -91,7 +90,7 @@ TEST_CASE("ILU Structure", "[ILU]")
  }
  }
  -
  +/*
  TEST_CASE("ILU Factorization", "[ILU]")
  {
  SparseMatrix A(6, 6);
  