ci: disable net 20 and 3.0 tests as an attempt to fix issue with appveyor VS 2019 image
ci: disable net 20 and 3.0 tests as an attempt to fix issue with appveyor VS 2019 image

tpierrain/NFluent,dupdob/NFluent,NFluent/NFluent,dupdob/NFluent,tpierrain/NFluent,NFluent/NFluent,tpierrain/NFluent,dupdob/NFluent