Change the spawn numbers of utility buildings

After looking at the issue of motels making by highway gas stations extremely rare; I realized that the very high numbers of utility buildings that map gen is required to spawn were the most likely reason of why I hadn't seen many (or in some cases any) apartment buildings, cathedrals, office towers, and public work buildings in my most recent playthroughs.

With this reduction, the large power substations share the public works building, and the SAI and small power substation share the same spawn numbers as the sewage treatment plant.