Increase RPG damage against building by 40% (about 2.5hp/shot)

It's an age-old unintuitive design that RPG missiles do so little damage to buildings.

Originally it's set to be like that because a group of grenadiers could take out buildings relentlessly at long range.

With the implementation of missile range, Grenadier RPG will have a limited range, nullifying any attempt to snip buildings.

Hence it's no longer necessary to hard-limit the damage of Grenadier RPG.