fixed compilation

Author: zerothi

presentations/04/hartree.tex

@@ -96,7 +96,7 @@ \subsection{Boundary conditions}
                 is. The guess is the Poisson solution \emph{without} charges, only the
                 boundary conditions.}}
 
-        \item \sisl\ has a tool to ease this. \shell{stoolbox ts-fft} may be used to
+        \item \texttt{sisl} has a tool to ease this. \texttt{stoolbox ts-fft} may be used to
         create a better boundary condition as direct input for TranSiesta.
 
       \end{itemize}