Allow Romans to build the sentry tower, revealing the new model from rP18754.
The faction couldn't build it before as the wooden tower added to all factions except Romans in rP16285 was logically a part of the palisade which Romans couldn't build either following rP11860.

Differential Revision: https://code.wildfiregames.com/D129
Patch By: fatherbushido
Accepted by: LordGood, scythetwirler, wowgetoffyourcellphone