Make asking for missing pieces in forms optional

app/views/contests/settings_onsite_edit.html.slim

@@ -10,13 +10,17 @@
       .form-check.form-switch
         = form.check_box :organizer_form, class: "form-check-input"
         = form.label :organizer_form
-      .form-text = t("activerecord.attributes.contest.organizer_form")
   .row.mt-3.mb-3
     .col
       .form-floating
         = form.text_field :code, autocomplete: "off", class: "form-control"
         = form.label :code, class: "required"
         .form-text = t("activerecord.attributes.contest.code_description")
+  .row.mt-1
+    .col
+      .form-check.form-switch
+        = form.check_box :missing_pieces, class: "form-check-input"
+        = form.label :missing_pieces
   .row.mt-4
     .col
       = form.submit t("helpers.buttons.update"), class: "btn btn-primary"