Localized "Featured Add-On" string is still in English for all languages

[peiying2]

Describe the problem and steps to reproduce it:

https://addons.mozilla.org/nl/firefox/collections/mozilla/featured-add-ons/ - first reported in bug 1417120 but it looks like the issue exists in all languages

What happened?

Localized string is not displayed on production, even though the string was translated several weeks ago.

What did you expect to happen?

Localized string displayed at this prominent spot.

Anything else we should know?

https://addons.mozilla.org/nl/firefox/collections/mozilla/featured-add-ons/ (change locale code, you will see the issue is common for all locales.

┆Issue is synchronized with this Jira Task