Replace p.fr-callout__text with div to avoid unauthorised nesting

app/views/commencer/show.html.haml

@@ -3,7 +3,7 @@
 .commencer.form
   - if !user_signed_in?
     = render Dsfr::CalloutComponent.new(title: t(".start_procedure"), heading_level: 'h2') do |c|
-      - c.with_body do
+      - c.with_html_body do
         = render partial: 'shared/france_connect_login', locals: { url: commencer_france_connect_path(path: @procedure.path, prefill_token: @prefilled_dossier&.prefill_token) }
         %ul.fr-btns-group.fr-btns-group--inline
           %li