reduce problem size + no matrix_free

test/blockstructured/poisson/poisson_vec.mini

 __name = blockstructured_poisson_vec
 
-cells = 10 10
+cells = 5 5
 extension = 1. 1.
 
 [wrapper.vtkcompare]
@@ -13,5 +13,4 @@ numerical_jacobian = 1
 compare_l2errorsquared = 1e-7
 blockstructured = 1
 number_of_blocks = 16
-vectorization_blockstructured = 1
-matrix_free = 1
+vectorization_blockstructured = 1
\ No newline at end of file