controllers: use template: rather than file: to render PDFs

ActionView now throws an error if a relative path is used with `file:`.

app/controllers/users/commencer_controller.rb

@@ -82,7 +82,7 @@ module Users
 
     def generate_empty_pdf(procedure)
       @dossier = procedure.new_dossier
-      s = render_to_string(file: 'dossiers/dossier_vide', formats: [:pdf])
+      s = render_to_string(template: 'dossiers/dossier_vide', formats: [:pdf])
       send_data(s, :filename => "#{procedure.libelle}.pdf")
     end
   end

app/controllers/users/dossiers_controller.rb

@@ -32,7 +32,7 @@ module Users
       respond_to do |format|
         format.pdf do
           @include_infos_administration = false
-          render(file: 'dossiers/show', formats: [:pdf])
+          render(template: 'dossiers/show', formats: [:pdf])
         end
         format.all
       end