Greeter help window not localized

When I select a non-English language and then click on a help button in the Greeter, I expected that I would see the help page in that language (if available). Instead, it is always opened in English.

Feature Branch: https://salsa.debian.org/tails-team/tails/merge_requests/39/commits

Related issues

Is duplicate of #6525 (closed)

Original created by @segfault on 17101 (Redmine)

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