config: fix zeitwekr warning when reloading the app

Turns out we need not only to load the Job constants later, but also
not to do the same work twice – otherwise we'll get a 

> ApiEntreprise::Job constant is already defined

when attempting to re-define the constant.

config/initializers/active_job_compatibility.rb

@@ -11,22 +11,24 @@
 # - but let's keep these for a while to make external integrators's life easier.
 # To keep some margin, let's say this file can be safely deleted in May 2021.)
 
-require 'excon'
-
 Rails.application.reloader.to_prepare do
-  module ApiEntreprise
-    Job = APIEntreprise::Job
-    AssociationJob = APIEntreprise::AssociationJob
-    AttestationFiscaleJob = APIEntreprise::AttestationFiscaleJob
-    AttestationSocialeJob = APIEntreprise::AttestationSocialeJob
-    BilansBdfJob = APIEntreprise::BilansBdfJob
-    EffectifsAnnuelsJob = APIEntreprise::EffectifsAnnuelsJob
-    EffectifsJob = APIEntreprise::EffectifsJob
-    EntrepriseJob = APIEntreprise::EntrepriseJob
-    ExercicesJob = APIEntreprise::ExercicesJob
-  end
+  if !defined?(ApiEntreprise)
+    require 'excon'
 
-  module Cron
-    FixMissingAntivirusAnalysis = FixMissingAntivirusAnalysisJob
+    module ApiEntreprise
+      Job = APIEntreprise::Job
+      AssociationJob = APIEntreprise::AssociationJob
+      AttestationFiscaleJob = APIEntreprise::AttestationFiscaleJob
+      AttestationSocialeJob = APIEntreprise::AttestationSocialeJob
+      BilansBdfJob = APIEntreprise::BilansBdfJob
+      EffectifsAnnuelsJob = APIEntreprise::EffectifsAnnuelsJob
+      EffectifsJob = APIEntreprise::EffectifsJob
+      EntrepriseJob = APIEntreprise::EntrepriseJob
+      ExercicesJob = APIEntreprise::ExercicesJob
+    end
+
+    module Cron
+      FixMissingAntivirusAnalysis = FixMissingAntivirusAnalysisJob
+    end
   end
 end