loosen generic guard on method for ResourceLoader

For more details see #22658

modules/mono/glue/Managed/Files/GD.cs

@@ -65,7 +65,7 @@ namespace Godot
             return ResourceLoader.Load(path);
         }
 
-        public static T Load<T>(string path) where T : Godot.Resource
+        public static T Load<T>(string path) where T : class
         {
             return (T) ResourceLoader.Load(path);
         }