As pointed out by @Stan in D2529, it is unbalanced you can train champion cavalry only at some but not all barracks. This patch inserts the barracks champions in the production list of the shared parent, which means that players who've researched the "unlock_champion_units" technology can train their champions at any captured enemy barracks, regardless the civ who built it, thus improving balance.
Likewise, it's unnecessary to specify the "unlock_champion_units" technology in individual specific barracks rather than the generic parent, because the technology files specify the civs that can research it; cf. D1941/rP22329.
Furthermore, it moves mace_champion_infantry_a_barracks.xml to mace_champion_infantry_barracks.xml and deletes mace_champion_infantry_e_barracks.xml, so Macedon can train them at captured enemy barracks and enemies can train theirs at mace barracks.