Update poll questions translatable fields

We need to replace ".title=" by ".title_#{locale}=" in one place because
for some reason globalize builds a new translation record when using the
latter but it doesn't build one when using the former.

config/locales/en/activerecord.yml

@@ -194,6 +194,8 @@ en:
         summary: "Summary"
         description: "Description"
         external_url: "Link to additional documentation"
+      poll/question/translation:
+        title: "Question"
       signature_sheet:
         signable_type: "Signable type"
         signable_id: "Signable ID"