Fix left-over in task

exercises/source-code-listings/task.tex

@@ -26,7 +26,7 @@ If you have questions, consult the \pkg{minted} or \pkg{listings} package docume
   \item Set the \mono{basicstyle} to a proper mono-spaced font (\mono{\textbackslash ttfamily \textbackslash small})
   \item Add line numbers.
   \item Change the keyword color to blue.
-  \item Include only lines 5 to 7.
+  \item Don't show special characters for spaces in strings.
 \end{enumerate}
 
 \exercisematerial{exercises/source-code-listings/source-code-listings}