Include default locale in fallbacks explicitly

We were getting a warning because it won't be included by default in
Rails 6.1:

DEPRECATION WARNING: Using I18n fallbacks with an empty `defaults` sets
the defaults to include the `default_locale`. This behavior will change
in Rails 6.1 . If you desire the default locale to be included in the
defaults, please explicitly configure it with
`config.i18n.fallbacks.defaults = [I18n.default_locale]` or
`config.i18n.fallbacks = [I18n.default_locale, {...}]`. If you want to
opt-in to the new behavior, use `config.i18n.fallbacks.defaults = [nil,
{...}] `.

config/application.rb

@@ -97,7 +97,7 @@ module Consul
       "zh-CN",
       "zh-TW"]
     config.i18n.available_locales = available_locales
-    config.i18n.fallbacks = {
+    config.i18n.fallbacks = [I18n.default_locale, {
       "ca"    => "es",
       "es-PE" => "es",
       "eu"    => "es",
@@ -107,7 +107,7 @@ module Consul
       "oc"    => "fr",
       "pt-BR" => "es",
       "val"   => "es"
-    }
+    }]
 
     config.i18n.load_path += Dir[Rails.root.join("config", "locales", "**[^custom]*", "*.{rb,yml}")]
     config.i18n.load_path += Dir[Rails.root.join("config", "locales", "custom", "**", "*.{rb,yml}")]