fix fixup.gd script error/warnings

Author: williamchange

scripts/fixup.gd

@@ -2,15 +2,14 @@
 extends EditorScript
 
 func _run():
-	var dir : Directory = Directory.new()
-	dir.open("res://addons/material_maker/nodes")
+	var dir : DirAccess = DirAccess.open("res://addons/material_maker/nodes")
 	dir.list_dir_begin() # TODOGODOT4 fill missing arguments https://github.com/godotengine/godot/pull/40547
 	var file_name = dir.get_next()
-	var loader = load("res://addons/material_maker/engine/loader.gd").new()
+	var _loader = load("res://addons/material_maker/engine/loader.gd").new()
 	while file_name != "":
 		if file_name.ends_with('.mmg'):
 			print("converting "+file_name)
 			var file_path : String = "res://addons/material_maker/nodes".path_join(file_name)
-			var g = mm_loader.load_gen(file_path)
+			var g = await mm_loader.load_gen(file_path)
 			mm_loader.save_gen(file_path, g)
 		file_name = dir.get_next()