Reduce mithril chest to gold chest size

Due to concerns about form appearance, reduce mithril chest size to avoid
its form exceeding screen height.  This reduces it to the same size as
the gold chest.  Having two chest types of the same size looks silly now,
but will be reasonable as soon as mithril chests get their long-planned
special features.

technic_chests/mithril_chest.lua

@@ -26,7 +26,7 @@ minetest.register_craft({
 
 technic.chests:register("Mithril", {
 	width = 15,
-	height = 7,
+	height = 6,
 	sort = true,
 	autosort = true,
 	infotext = false,
@@ -36,7 +36,7 @@ technic.chests:register("Mithril", {
 
 technic.chests:register("Mithril", {
 	width = 15,
-	height = 7,
+	height = 6,
 	sort = true,
 	autosort = true,
 	infotext = false,