Balance adjust: Return LTNK dmg. vs. wood to 75%

It seemed that the tanks were inept at hurting buildings and needed a boost. However, after playtesting, it's clear that Nod's flame tank is already exceptional at destroying buildings, and the recon bikes are quite decent at it, too. Thus, the light tank's effectiveness at killing buildings is overlapping with the flame tank (same tech level & cost), making most Nod units effective at hurting buildings. So, I think this is in order to preserve distinct roles among the vehicles.
Reduce grenadier vs. wood 75% -> 50%

Grenadiers actually do more damage than flamethrowers vs. buildings, which is counter-intuitive and not in keeping with flavour and design intent. They should be good vs. buildings, but not quite this good, especially given that they are cheaper than flamethrowers. This nerf still allows them to be effective at taking out buildings, but not quite as blindingly fast at destroying them.
Merge pull request #5286 from psydev/patch-1

Balance adjust: Return LTNK dmg. vs. wood to 75%