Make Lint/UselessAccessModifier aware of ActiveSupport::Concern

[Earlopain]

Ref rubocop/rubocop#7298

Allow code like this by default:

module Foo
  extend ActiveSupport::Concern

  private

  def private_instance_bar
  end

  class_methods do
    private

    def private_class_bar
    end
  end
end

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