Make dry grass spread on default:dirt again (#2687)

mods/default/functions.lua

@@ -501,7 +501,7 @@ end
 
 
 --
--- Convert dirt to something that fits the environment
+-- Convert default:dirt to something that fits the environment
 --
 
 minetest.register_abm({
@@ -510,6 +510,7 @@ minetest.register_abm({
 	neighbors = {
 		"air",
 		"group:grass",
+		"group:dry_grass",
 		"default:snow",
 	},
 	interval = 6,
@@ -538,6 +539,8 @@ minetest.register_abm({
 			minetest.set_node(pos, {name = "default:dirt_with_snow"})
 		elseif minetest.get_item_group(name, "grass") ~= 0 then
 			minetest.set_node(pos, {name = "default:dirt_with_grass"})
+		elseif minetest.get_item_group(name, "dry_grass") ~= 0 then
+			minetest.set_node(pos, {name = "default:dirt_with_dry_grass"})
 		end
 	end
 })