Update for new Package versions #475
Description
Not sure how much you have followed stuff, but there has been a shake-up in ModelingToolkit (https://discourse.julialang.org/t/modelingtoolkit-v11-library-split-and-licensing-community-feedback-requested/134396). For packages like Catalyst and SI there is no real big difference, however, from now on ModelingToolkitBase (https://github.com/SciML/ModelingToolkit.jl/tree/master/lib/ModelingToolkitBase) is the package to use. I think, in principle, it is just to sitch all uses of ModelingToolkit to ModelingToolkitBase.
With that, there are now also new versions of Symbolics and SymbolicUtils. Hopefully, the systemj should be fairly stable going forward from this. @AayushSabharwal have done the new udpates, so he should hopefully be able to help if there are any troubles in the transition.