Includes are not internationalized

[agektmr]

For example this article: https://developer.chrome.com/ja/docs/privacy-sandbox/attribution-reporting-experiment/

Everything is translated except "Join the discussion" and "Get updates".

Looking at the markdown, they are included by:

{% include 'content/privacysandbox-partials/ar-join-discussion-long.njk' %}

{% include 'content/privacysandbox-partials/ar-get-updates.njk' %}

We need to internationalize things under _includes/contents.