wallet: fix boost::get usage with boost 1.58

src/wallet/rpcwallet.cpp

@@ -2330,7 +2330,7 @@ Value listunspent(const Array& params, bool fHelp)
         if (pk.IsPayToScriptHash()) {
             CTxDestination address;
             if (ExtractDestination(pk, address)) {
-                const CScriptID& hash = boost::get<const CScriptID&>(address);
+                const CScriptID& hash = boost::get<CScriptID>(address);
                 CScript redeemScript;
                 if (pwalletMain->GetCScript(hash, redeemScript))
                     entry.push_back(Pair("redeemScript", HexStr(redeemScript.begin(), redeemScript.end())));