Zinc rareness FIX(?) (#333)

* Zinc rareness FIX(?)

I created the issue and i will fix it. But still idk if this really helps. (It helped me)
At least it will make it more common in -32 and 2 Y distance. To compare its like in between iron and coal i belive.

* Update oregen.lua

technic_worldgen/oregen.lua

@@ -54,13 +54,11 @@ minetest.register_ore({
 	ore_type         = "scatter",
 	ore              = "technic:mineral_zinc",
 	wherein          = "default:stone",
-	clust_scarcity   = 9*9*9,
+	clust_scarcity   = 8*8*8,
 	clust_num_ores   = 5,
 	clust_size       = 7,
 	y_min       = -32,
-	y_max       = 2,
-	noise_params     = lead_params,
-	noise_threshhold = lead_threshhold,
+	y_max       = 2
 })
 
 minetest.register_ore({