Bug 24972: Remove de-DE installer data

Bug 24972: Remove de-DE installer data

With installer data in YAML format and it's translations,
there are no need for localized installer files.

This patch removes de-DE installer files.

1) Apply the patch
2) Translate to de-DE
   cd misc/translator
   ./translate update de-DE
   ./translate install de-DE
3) Do a clean install using de-DE,
   check no problems during install
4) Verify MARC21 frameworks, they must
   be translated

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>