config: Increase mountain process efficiency from 75% to 100%
Each point of gold resource is worth 5d. Except for mountains, where
it's just 3.75d. This is because a mountain's process efficiency is
only 75%. Has been that way since Empire 3 made mountains mine gold.
This is actually a needless complication: a sector with 75% process
efficiency produces just like one with 100% process efficiency and 75%
of the resource.
Increase mountain process efficiency to 100%. Deities may want to
compensate by adjusting mountains' gold resources.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>