mulit: use min relay fee error

lnwallet/btcwallet/btcwallet.go

@@ -1133,7 +1133,9 @@ func mapRpcclientError(err error) error {
 	// If the wallet reports that fee requirements for accepting the tx
 	// into mempool are not met, convert it to our internal ErrMempoolFee
 	// and return.
-	case errors.Is(err, chain.ErrMempoolMinFeeNotMet):
+	case errors.Is(err, chain.ErrMempoolMinFeeNotMet),
+		errors.Is(err, chain.ErrMinRelayFeeNotMet):
+
 		return fmt.Errorf("%w: %v", lnwallet.ErrMempoolFee, err.Error())
 	}