[Tails-l10n] (review)[de] 2.9.1 release notes

Hi,
I translated the release notes for the latest version.
Please review:

https://gitlab.com/spriver/tails.git
branch: de_tails_291
HEAD commit: 88c7303 Initial translation

Affected files:
wiki/src/news/version_2.9.1.de.po
wiki/src/security/Numerous_security_holes_in_2.7.1.de.po


Cheers!
spriver