[wp/doc] Fixes Why3 version

src/plugins/wp/doc/manual/wp_plugin.tex

@@ -34,7 +34,7 @@ The recommended versions for external provers are:
   \begin{tabular}{crlc}
     Prover & Versions & Download &\\
     \hline
-    \textsf{Why3} & \verb|1.2.0| &
+    \textsf{Why3} & \verb|1.3.1| &
     \url{http://why3.lri.fr} & \cite{Why3}\\
     \textsf{Alt-Ergo} & \verb|2.0.0|  &
     \url{http://alt-ergo.ocamlpro.com} & \cite{AltErgo2006}\\
@@ -48,7 +48,7 @@ Other versions might be supported as well, typically, as far as we know:
 \begin{itemize}
 \item \textsf{Alt-Ergo} \verb+2.2.0+ and \verb+2.3.0+, although distributed under a non-commercial licence.
 % \item \textsf{Coq} \verb+8.7.2+ and \verb+8.8.2+, although proof scripts compatibility can be an issue.
-\item \textsf{Why3} \verb+1.0.0+ and \verb+1.1.1+, although only \verb+1.2.0+ is provided with Coq support.
+\item \textsf{Why3} \verb+1.3.1+.
 \end{itemize}
 
 Other provers, like \textsf{Coq}, \textsf{Gappa}, \textsf{Z3}, \textsf{CVC3},