Fix StringSort precision (#99)

Fix #75

Author: GabrielDosReis

ltx/exprs.tex

@@ -620,7 +620,7 @@ \subsection{\valueTag{ExprSort::String}}
 the string table.  A \type{StringIndex} value, like any abstract reference, is a 32-bit value:
 \begin{figure}[H]
   \centering
-	\absref{4}{StringSort}
+	\absref{3}{StringSort}
   \caption{\type{StringIndex}: Abstract reference of string constant}
   \label{fig:ifc-string-index}
 \end{figure}