This removes the last occurences of `::Chain(State)Active` in the code after D11704, D11742 and D11744 are landed. There are some remaining occurences in comments, which are removed in a later backport (core#23258)
I checked in the codebase that these methods are only called on the active chainstate. It does not make much sense to finalize blocks in a chain base on the state of some other chain anyway.