Make it easier to know destroy_field is an input

By using the input and finding it by its name, it's easier to see the
difference between this input and the delete-language link.

app/assets/javascripts/globalize.js.coffee

@@ -48,7 +48,7 @@ App.Globalize =
     )
 
   destroy_locale_field: (locale) ->
-    $(".destroy-locale[data-locale=" + locale + "]")
+    $("input[id$=_destroy][data-locale=" + locale + "]")
 
   site_customization_enable_locale_field: (locale) ->
     $("#enabled_translations_" + locale)

app/helpers/translatable_form_helper.rb

@@ -13,7 +13,6 @@ module TranslatableFormHelper
             @template.content_tag :div, translations_options(translations_form.object, locale) do
               @template.concat translations_form.hidden_field(
                 :_destroy,
-                class: "destroy-locale",
                 data: { locale: locale })
 
               @template.concat translations_form.hidden_field(:locale, value: locale)