[gameplay-a24] Allow training all barracks champions at captured barracks.

Before this change, civilisation could train champions in captured barracks only if captured barracks allowed to train that unit, what was not always the case so some champions were allowed to be trained in captured barracks and some was not.

Differential Revision: https://code.wildfiregames.com/D2547
Patch by: Nescio
Reviewed by: ValihrAnt