Update 07_namespaces.tex

Line92: sub-namespace

lecture/07_namespaces.tex

@@ -89,7 +89,7 @@ If you have a complicated or multiple enclosed namespaces, you can introduce a n
 %
 \begin{minted}{c++}
 namespace Q {
-  namespace V {  // sub-namensraum of Q
+  namespace V {  // sub-namespace of Q
     void f() {}; // declaration of Q::V::f
   }
 }