Merge settings & core indexes into a single nav

app/views/contestants/_form.html.slim

@@ -1,7 +1,3 @@
-.row
-  .col
-    h3 Informations
-
 = form_with model: contestant, url: url, method: method do |form|
   .row.mb-3
     .col
@@ -15,7 +11,7 @@
         = form.label :email
     .form-text
       = t("activerecord.attributes.contestant.email_description")
-  - if @contest.categories
+  - if @contest.categories && method == :patch
     .row.mt-4
       .col
         - @contest.categories.each do |category|