Use setting to generate Quartz ore

mods/MAPGEN/mcl_biomes/init.lua

@@ -2043,6 +2043,7 @@ local function register_dimension_ores()
 	})
 
 	-- Nether quartz
+	if minetest.settings:get("mcl_generate_ores") == "true" then
 		minetest.register_ore({
 			ore_type       = "scatter",
 			ore            = "mcl_nether:quartz_ore",
@@ -2063,6 +2064,7 @@ local function register_dimension_ores()
 			y_min = mcl_vars.mg_nether_min,
 			y_max = mcl_vars.mg_nether_max,
 		})
+	end
 
 	-- Lava springs in the Nether
 	minetest.register_ore({