multi: bump btcd version.

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

lnrpc/invoicesrpc/addinvoice.go

@@ -587,7 +587,7 @@ func AddInvoice(ctx context.Context, cfg *AddInvoiceConfig,
 
 			return ecdsa.SignCompact(
 				ephemKey, chainhash.HashB(msg), true,
-			)
+			), nil
 		},
 	})
 	if err != nil {