views: tell an attestation will be sent only if it is true

Previously the message stating "an attestation will be sent" was
displayed even when the attestation was disabled.

app/views/instructeurs/dossiers/_state_button_motivation.html.haml

@@ -6,6 +6,7 @@
   = form_tag(terminer_instructeur_dossier_path(dossier.procedure, dossier), remote: true, method: :post, class: 'form') do
     - if title == 'Accepter'
       = text_area :dossier, :motivation, class: 'motivation-text-area', placeholder: placeholder, required: false
+      - if dossier.procedure.attestation_template&.activated?
         %p.help
           L'acceptation du dossier envoie automatiquement une attestation à l'usager.
 

spec/views/instructeur/dossiers/_state_button_motivation.html.haml_spec.rb

@@ -20,6 +20,7 @@ describe 'instructeurs/dossiers/state_button_motivation.html.haml', type: :view
   end
 
   context 'without an attestation preview' do
+    it { expect(rendered).not_to have_text("envoie automatiquement une attestation") }
     it { expect(rendered).not_to have_text("Voir l'attestation") }
   end
 end