[Tails-l10n] [de] Broken link

Hi,

there is a broken link on the bottom of
https://tails.boum.org/about/index.de.html

{{{
Sehen Sie die Danksagungen und ähnliche
Projekte|doc/about/acknowledgments_and_similar_projects]].
}}}

Right now I don't have a clone of the Git repo, so I can't fix it
myself, but if nobody does it, I might do it soonish.

Cheers!
u.