Remove the dossier number from the dossier processing popover

- One popup_title wasn’t written so that its
  combination with the dossier number made sense

- The number is already visible on the page

- The number is not that important to make a
  decision (the context it adds does not have
  so much value)

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

@@ -1,7 +1,7 @@
 .motivation{ class: popup_class }
   %h3
     %span.icon{ class: popup_class }
-    #{popup_title} nº #{dossier.id}
+    #{popup_title}
 
   = form_tag(terminer_dossier_path(dossier.procedure, dossier), method: :post, class: 'form') do
     = text_area :dossier, :motivation, class: 'motivation-text-area', placeholder: 'Rédigez votre motivation ici (facultative)'