regression: email notification about merge contains unevaluated `sprintf` statement (plain text only, not html)

In the attached screenshot of the plain text view (in thunderbird) of a gitlab notification there is an unevaluated string

sprintf(s ('Notify|Author: %{author_name}'), { author_name: sanitize_name(@merge_request.author_name) })

I received this today (2022-04-08T10:26 CEST). Checking a random other notification from a few days ago, it says in that place

Author: ....

(with the name of the author)