refactor: turn on simplification in OPF benchmark

Author: AayushSabharwal

benchmarks/OptimizationFrameworks/optimal_powerflow.jmd

@@ -722,7 +722,7 @@ function build_opf_mtk_prob(dataset)
     end
 
     optsys = ModelingToolkit.OptimizationSystem(loss, vars, [], constraints=cons, name=:rosetta)
-    optsys = ModelingToolkit.complete(optsys)
+    optsys = ModelingToolkit.structural_simplify(optsys)
     u0map = [Num(k) => 0.0 for k in collect(unknowns(optsys))]
     ks = collect(Num.(unknowns(optsys)))
     for key in keys(ref[:bus])