Updated german translation

[tweimer]

Check if this PR fulfills these requirements:

• [x] My changes respect the Kodi add-on development rules
• [x] I have read the CONTRIBUTING document.
• [x] I made sure there wasn't another Pull Request opened for the same update/change
• [x] I have successfully tested my changes locally

Types of changes

• [ ] New feature (non-breaking change which adds functionality)
• [ ] Feature change (non-breaking change which changes behaviour of an existing functionality)
• [x] Improvement (non-breaking change which improves functionality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Refactor (non-breaking performance or readability improvements)

Description

See #306