nlstep tests: unbreak NSA(TrustRegion) order assertions that now pass

[singhharsh1708]

Four @test_broken order assertions in modelingtoolkit/nlstep_tests.jl now pass, so the MTK lane reports them as Unexpected Pass and errors out:

Unexpected Pass
Expression: abs(sim.𝒪est[:l∞] - 2) < 0.2
Got correct result, please change to @test if no longer broken.

All four are NonlinearSolveAlg(TrustRegion()) convergence-order checks — TRBDF2 and QNDF2, in both the non-autonomous and autonomous Robertson blocks. They were the failures behind #3807 and #3818, and the recent NonlinearSolve releases (SciML/NonlinearSolve.jl#1010 recomputing the trust-region radius on reinit!, plus #1008) fixed them upstream.

This flips those four to @test. The two KenCarp4 order-4 assertions still fail and stay @test_broken.

Verified on a clean checkout of master (8ed2f7a): before, 19 passed, 0 failed, 4 errored, 2 broken; after, 23 passed, 2 broken, 0 errored. The same 4 errors show up on the MTK lane of every open PR that touches this sublibrary, which is what makes that lane red.

AI Disclosure

Claude assisted with this work.

[ChrisRackauckas]

I already got these running