Improve error message in z_sendmany if tx is estimated to be too large

The previous error message was incorrect, it could be too many inputs
or a combination of too many inputs and outputs and also did not report
the estimated size.

src/wallet/rpcwallet.cpp

@@ -5311,7 +5311,7 @@ UniValue z_sendmany(const UniValue& params, bool fHelp, const CPubKey& mypk)
     }
     txsize += CTXOUT_REGULAR_SIZE * taddrRecipients.size();
     if (txsize > max_tx_size) {
-        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Too many outputs, size of raw transaction would be larger than limit of %d bytes", max_tx_size ));
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Size of raw transaction %d would be larger than limit of %d bytes", txsize, max_tx_size ));
     }
 
     // Minimum confirmations