why3: use why3.version in withProvers

I was getting an error that 'name' was not defined, which was being
caused by pname being passed in without a version.

Using the version of the why3 package resolves this.

pkgs/applications/science/logic/why3/with-provers.nix

@@ -13,6 +13,7 @@ let configAwkScript = runCommand "why3-conf.awk" { inherit provers; }
 in
 stdenv.mkDerivation {
   pname = "${why3.pname}-with-provers";
+  version = why3.version;
 
   nativeBuildInputs = [ makeWrapper ];
   buildInputs = [ why3 ] ++ provers;