Simplify code involving Globalize.locale

We don't need to set this value. In commit f2ef27d3 I made a mistake
thinking `Globalize.locale` and `I18n.locale` should always be in sync,
but they're actually automatically in sync when `Globalize.locale` is
`nil`.

So the best way to avoid any issues is not to assign `Globalize.locale`,
and use `Globalize.with_locale` where necessary instead.

app/controllers/admin/site_customization/information_texts_controller.rb

@@ -18,8 +18,9 @@ class Admin::SiteCustomization::InformationTextsController < Admin::SiteCustomiz
             next
           else
             text = I18nContent.find_or_create_by!(key: content[:id])
-            Globalize.locale = locale
-            text.update!(value: value)
+            Globalize.with_locale(locale) do
+              text.update!(value: value)
+            end
           end
         end
       end