[#2772] Avoid overriding initialize in subclasses

lib/tasks/2018_07_31_nutriscore.rake

@@ -9,12 +9,7 @@ namespace :'2018_07_31_nutriscore' do
     destination_procedure = Procedure.find(destination_procedure_id)
 
     mapping = Class.new(Tasks::DossierProcedureMigrator::ChampMapping) do
-      def initialize(source_procedure, destination_procedure)
-        super
-        setup_champ_mapping
-      end
-
-      def setup_champ_mapping
+      def setup_mapping
         siret_order_place = 2
         fonction_order_place = 9
         zone_geographique_header_order_place = 18

lib/tasks/dossier_procedure_migrator.rb

@@ -12,6 +12,8 @@ module Tasks
         @source_to_destination_mapping = {}
         @source_champs_to_discard = Set[]
         @destination_champ_computations = []
+
+        setup_mapping
       end
 
       def check_source_destination_champs_consistency