Remove classDef from templates

This is only required if one wants to implement direct instances based on the templates without derivation. But, in our case, were always derive it is unecessary and also causes issues. Hence, I removed it with this commit.

Dear @f.uhlig, @v.friese, @p.-a.loizeau, @praisig,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

merged