multi: bump btcd version.

The new SignCompact return values had to be adopted across the
code base.

invoices/test_utils.go

@@ -4,7 +4,6 @@ import (
 	"crypto/rand"
 	"encoding/binary"
 	"encoding/hex"
-	"fmt"
 	"sync"
 	"testing"
 	"time"
@@ -69,11 +68,7 @@ var (
 	testMessageSigner = zpay32.MessageSigner{
 		SignCompact: func(msg []byte) ([]byte, error) {
 			hash := chainhash.HashB(msg)
-			sig, err := ecdsa.SignCompact(testPrivKey, hash, true)
-			if err != nil {
-				return nil, fmt.Errorf("can't sign the "+
-					"message: %v", err)
-			}
+			sig := ecdsa.SignCompact(testPrivKey, hash, true)
 
 			return sig, nil
 		},