[Tails-l10n] [de] Tails Installer translation

Hi,

I've been told by a user there is a translation mistake in Tails
Installer in german:

after installation is done a window appeares. there is language
translation faulty: "installation done. press button OK" but there is
no "OK" Button, its a "CLOSE" button. "Schließen"

Cheers.