Remove support of function arguments debugging from spec

spec/07.debugging.tex

@@ -20,7 +20,7 @@ \chapter{Debugging Support}
   \end{itemize}
 \item stepping over/into;
 \item inspecting the values of global variables by their source names;
-\item inspecting the values of function arguments and local variables (include those in nested scopes) by their source names;
+\item inspecting the values of local variables (include those in nested scopes) by their source names;
 \item inspecting the values in closures by their indices; the indices for closure elements can be found in stack machine
   program dump (option "\texttt{-ds}", see Section~\ref{sec:driver}).
 \end{itemize}