Fix toolchain frametitle

VL1.tex

@@ -672,7 +672,7 @@ Haskell is very powerful and can be used for pretty much anything. However, ther
 \section{6. Toolchain}
 
 \begin{frame}
-\frametitle{13. Toolchain}
+\frametitle{6. Toolchain}
 How to get started? You need:
 \begin{itemize}
 \item \textbf{GHC}: this is the Haskell compiler