fix: fix incorrect folding in `substitute` in `OptimizationSystem`#3475

ChrisRackauckas merged 1 commit intoSciML:masterSciML/ModelingToolkit.jl:masterfrom

AayushSabharwal:as/fix-optsysAayushSabharwal/ModelingToolkit.jl:as/fix-optsysCopy head branch name to clipboard