[de_DE translation] minor bugfix

There is small translation error in the de_DE version.

This would be the correct translation:

#: includes/emailpetition.php:89
#: includes/widget.php:227
msgid "Confirm Email"
msgstr "Best?tigen Sie Ihre Email

Could you incorporate this fix in one of your next releases?

https://www.ads-software.com/extend/plugins/speakup-email-petitions/