Exclude Towers from Town->City phase requirements.
Towers, unlike walls, palisades, and outposts, counted towards the required Town Phase structures for City Phase. Given the requirement to build 4 structures, this pushed players into making them.
This removes that, and lowers the requirement to 3.
Patch by: Nescio
Accepted By: ValihrAnt, borg-, wowgetoffyourcellphone, wraitii
Differential Revision: https://code.wildfiregames.com/D3686