Remove nonlinear matrix free DG

test/nonlinear/nonlinear_matrix_free_dg.mini

 __name = nonlinear_matrix_free_dg_{__exec_suffix}
-__exec_suffix = numdiff, symdiff | expand num
+__exec_suffix = symdiff
 
 lowerleft = 0.0 0.0
 upperright = 1.0 1.0
@@ -11,7 +11,7 @@ name = {__name}
 extension = vtu
 
 [formcompiler]
-numerical_jacobian = 1, 0 | expand num
+numerical_jacobian = 0
 matrix_free = 1
 exact_solution_expression = g
 compare_l2errorsquared = 1e-2