Fix depwarn

Author: YingboMa

test/structural_transformation/tearing.jl

@@ -218,8 +218,8 @@ u0 = [mass.s => 0.0
       mass.v => 1.0]
 
 sys = structural_simplify(ms_model)
-@test sys.jac[] === ModelingToolkit.EMPTY_JAC
-@test sys.tgrad[] === ModelingToolkit.EMPTY_TGRAD
+@test ModelingToolkit.get_jac(sys)[] === ModelingToolkit.EMPTY_JAC
+@test ModelingToolkit.get_tgrad(sys)[] === ModelingToolkit.EMPTY_TGRAD
 prob_complex = ODAEProblem(sys, u0, (0, 1.0))
 sol = solve(prob_complex, Tsit5())
 @test all(sol[mass.v] .== 1)