Switch siunitx Package to German Locale

Another step that was forgotten when the code was copied from an
English document.

instructions/zusatzanleitung.tex

@@ -10,7 +10,7 @@
 \usepackage[utf8x]{inputenc}
 \usepackage{pdfpages}
 \usepackage[colorlinks=true,linkcolor=blue]{hyperref}
-\usepackage[binary-units]{siunitx}
+\usepackage[binary-units,locale=DE]{siunitx}
 \usepackage{fancyvrb}
 \usepackage{fvextra}
 \usepackage[long,nodayofweek]{datetime}