Fix Regression_II: use TSRKC3() directly instead of OrdinaryDiffEq.OrdinaryDiffEqStabilizedRK.TSRKC3() (#3450)

`OrdinaryDiffEqStabilizedRK` is not a submodule of `OrdinaryDiffEq` on v7
(the main module only re-exports a small set of algorithms). The test file
already imports `OrdinaryDiffEqStabilizedRK` on line 3, and `TSRKC3` is
exported from it, so just use the bare name.

Co-authored-by: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

test/regression/iipvsoop_tests.jl

@@ -146,7 +146,7 @@ rosenbrock_algs = [
     @test sol_ip.t ≈ sol_scalar.t && sol_ip[1, :] ≈ sol_scalar.u
 end
 
-rkc_algs = [RKC(), ROCK2(), ROCK4(), SERK2(), OrdinaryDiffEq.OrdinaryDiffEqStabilizedRK.TSRKC3()]
+rkc_algs = [RKC(), ROCK2(), ROCK4(), SERK2(), TSRKC3()]
 
 @testset "Algorithm $(nameof(typeof(alg)))" for alg in rkc_algs
     println(nameof(typeof(alg)))