Ensure i18n matches options (#2358)

* Add failing spec showing that human_locales does not match what i18n knows about

* Add missing `ar` key for arabic to human locales

* Remove duplicate `id` key from available locales

* Sort keys in human locales list

* Add spec for human_locale helper

app/helpers/settings_helper.rb

@@ -3,29 +3,30 @@
 module SettingsHelper
   HUMAN_LOCALES = {
     en: 'English',
+    ar: 'عربى',
+    bg: 'Български',
     de: 'Deutsch',
-    es: 'Español',
     eo: 'Esperanto',
+    es: 'Español',
+    fi: 'Suomi',
     fr: 'Français',
     hr: 'Hrvatski',
     hu: 'Magyar',
+    id: 'Bahasa Indonesia',
     io: 'Ido',
     it: 'Italiano',
+    ja: '日本語',
     nl: 'Nederlands',
     no: 'Norsk',
     oc: 'Occitan',
     pl: 'Polszczyzna',
     pt: 'Português',
     'pt-BR': 'Português do Brasil',
-    fi: 'Suomi',
     ru: 'Русский',
     uk: 'Українська',
-    ja: '日本語',
     'zh-CN': '简体中文',
     'zh-HK': '繁體中文（香港）',
     'zh-TW': '繁體中文（臺灣）',
-    bg: 'Български',
-    id: 'Bahasa Indonesia',
   }.freeze
 
   def human_locale(locale)