procedure: move description to views/shared

Now that the description is used not only in the layout, but also in the
procedure form, better to make it an official shared partial.

app/views/layouts/procedure_context.html.haml

@@ -6,7 +6,7 @@
 
       .column.procedure-preview
         - if procedure
-          = render partial: 'layouts/commencer/procedure_description', locals: { procedure: procedure }
+          = render partial: 'shared/procedure_description', locals: { procedure: procedure }
         - else
           = render partial: 'layouts/commencer/no_procedure'
 

app/views/new_administrateur/procedures/edit.html.haml

@@ -21,4 +21,4 @@
       .procedure-form__preview.sticky--top
         %h3.procedure-form__preview-title Aperçu
         .procedure-preview
-          = render partial: 'layouts/commencer/procedure_description', locals: { procedure: @procedure }
+          = render partial: 'shared/procedure_description', locals: { procedure: @procedure }

app/views/new_administrateur/procedures/new.html.haml

@@ -21,4 +21,4 @@
       .procedure-form__preview.sticky--top
         %h3.procedure-form__preview-title Aperçu
         .procedure-preview
-          = render partial: 'layouts/commencer/procedure_description', locals: { procedure: @procedure }
+          = render partial: 'shared/procedure_description', locals: { procedure: @procedure }