make_typed_semi_sequence doesn't exist

[Forthoney]

I am realizing this only now, but there is a function called make_typed_semi_sequence being used in the preprocess_ast_cases. This used to also be in ast_to_ast which is where the logic used to live. But there exists no function in the repo with this name. The closest is make_semi_sequence. I would appreciate if one of the people familiar with the repo for a longer time would confirm this is indeed the case @angelhof @mgree @nvasilakis