databases/ruby-awesome_nested_set: update to 3.3.1

3.3.1
* Add belongs_to :polymorphic key option only when used [Filippo Liverani](https://github.com/filippoliverani)
* [Compare to 3.3.0](https://github.com/collectiveidea/awesome_nested_set/compare/v3.3.0...v3.3.1)

3.3.0
* Update for compatibility with Rails 6.1 which no longer inherits scoping
  (Messages of the form "DEPRECATION WARNING: Class level methods will no longer inherit scoping from ...") [Marc Rohloff](https://github.com/marcrohloff)
* Fix ruby 2.7 keyword parameters deprecation warning [Krisdigital](https://github.com/krisdigital)
* [Compare to 3.2.1](https://github.com/collectiveidea/awesome_nested_set/compare/v3.2.1...v3.3.0)

(taca)