po: Fix a string in de and nl. Mark a string in ro and sk fuzzy.

These wrong translations are propably due to accidently removing a
fuzzy mark.

A German translation (gpgsm audit feature) was actually reversed.

A Dutch translation has an unused ": %s" at the end.

I am not 100% of the Romanian and Slovak strings, thus I marked them
as fuzzy.

• GnuPG-bug-id: T3619
• Signed-off-by: Werner Koch <wk@gnupg.org>