Clean up sage_setup.library_order #30579
Description
Follow-up from #29702, #29706:
We remove code that duplicated the function of sage.env.cython_aliases
CC: @jhpalmieri @kiwifb @dimpase
Component: build
Author: Matthias Koeppe
Branch/Commit: 49cd771
Reviewer: Dima Pasechnik
Issue created by migration from https://trac.sagemath.org/ticket/30579