Correct german string
Correct german string

reported wrong from beta user.
Correction also done on Crowdin for `master`
matej116/cgeo,rsudev/c-geo-opensource,rsudev/c-geo-opensource,tobiasge/cgeo,tobiasge/cgeo,cgeo/cgeo,cgeo/cgeo,auricgoldfinger/cgeo,matej116/cgeo,auricgoldfinger/cgeo,rsudev/c-geo-opensource,S-Bartfast/cgeo,matej116/cgeo,auricgoldfinger/cgeo,cgeo/cgeo,cgeo/cgeo,S-Bartfast/cgeo,tobiasge/cgeo,S-Bartfast/cgeo