change the way we set the finished_at on batch operation job to fix alert display bug

spec/models/batch_operation_spec.rb

@@ -98,15 +98,6 @@ describe BatchOperation, type: :model do
           .not_to change { batch_operation.reload.run_at }
       end
     end
-
-    context 'when it is the last job' do
-      it 'sets finished_at' do
-        expect { batch_operation.track_processed_dossier(true, dossier) }
-          .to change { batch_operation.reload.finished_at }
-          .from(nil)
-          .to(anything)
-      end
-    end
   end
 
   describe '#dossiers_safe_scope (with archiver)' do