review: move Prefillable to concern directory

app/models/concerns/dossier_prefillable_concern.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-module Dossier::Prefillable
+module DossierPrefillableConcern
   extend ActiveSupport::Concern
 
   def prefill!(champs_public_attributes)

app/models/dossier.rb

@@ -43,11 +43,10 @@
 #  user_id                                            :integer
 #
 class Dossier < ApplicationRecord
-  include Dossier::Prefillable
-
   self.ignored_columns = [:en_construction_conservation_extension]
   include DossierFilteringConcern
   include DossierRebaseConcern
+  include DossierPrefillableConcern
 
   enum state: {
     brouillon:       'brouillon',

spec/models/concern/dossier_prefillable_concern_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe Dossier::Prefillable do
+RSpec.describe DossierPrefillableConcern do
   describe '.prefill!' do
     let(:procedure) { create(:procedure, :published) }
     let(:dossier) { create(:dossier, :brouillon, procedure: procedure) }