l10n: de.po: fix typo

Reported-by: Hartmut Henkel
Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
l10n: de.po: improve message when switching branches

Suggested-by: Stefan Beller <stefanbeller@gmail.com>
Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>