Move back to dotnet 5.0 from 6.0

.../Debug/netcoreapp5.0/Tests/ind-simpl/Proof_error_39.proof

...coreapp5.0/Tests/ind-simpl/Proof_not_parsable_IH_nd.proof

...ion/bin/Debug/netcoreapp5.0/Tests/ind-simpl/Task_Bsp.task

...on/bin/Debug/netcoreapp5.0/Tests/ind-simpl/Task_Bsp2.task

...ktion/bin/Debug/netcoreapp5.0/Tests/ind-struk/ADT_Bsp.adt

...n/Debug/netcoreapp5.0/Tests/ind-struk/Proof_correct.proof

.../Debug/netcoreapp5.0/Tests/ind-struk/Proof_error_22.proof

.../Debug/netcoreapp5.0/Tests/ind-struk/Proof_error_42.proof

.../Debug/netcoreapp5.0/Tests/ind-struk/Proof_error_43.proof

...ion/bin/Debug/netcoreapp5.0/Tests/ind-struk/Task_Bsp.task

...Induktion/bin/Debug/netcoreapp5.0/Tests/lemma/ADT_Bsp.adt

.../Debug/netcoreapp5.0/Tests/lemma/Proof_T2_correct_0.proof

...ug/netcoreapp5.0/Tests/lemma/Proof_T3,4_error_20,21.proof

...Debug/netcoreapp5.0/Tests/lemma/Proof_T3_error_21-2.proof

...n/Debug/netcoreapp5.0/Tests/lemma/Proof_T3_error_21.proof

...n/Debug/netcoreapp5.0/Tests/lemma/Proof_T3_error_22.proof

...n/Debug/netcoreapp5.0/Tests/lemma/Proof_T3_error_23.proof

...ebug/netcoreapp5.0/Tests/lemma/Proof_T4_error_20,21.proof

...bin/Debug/netcoreapp5.0/Tests/lemma/Proof_correct_0.proof

...bin/Debug/netcoreapp5.0/Tests/lemma/Proof_correct_1.proof