test: fix adif roundtrip_test writeRecord calls for new allow-set param

writeRecord gained a fourth `allow map[string]bool` argument in the export
field-picker change; the round-trip test still called it with three. Pass nil
(no field filtering — the historical behaviour).

internal/adif/roundtrip_test.go

@@ -34,7 +34,7 @@ func TestPromotedFieldsRoundTrip(t *testing.T) {
 	var buf bytes.Buffer
 	bw := bufio.NewWriter(&buf)
 	bw.WriteString("<EOH>\n")
-	writeRecord(bw, in, true)
+	writeRecord(bw, in, true, nil)
 	bw.Flush()
 
 	var rec Record
@@ -115,7 +115,7 @@ func TestStandardExportDropsNonStandard(t *testing.T) {
 func renderRecord(q qso.QSO, includeApp bool) string {
 	var buf bytes.Buffer
 	bw := bufio.NewWriter(&buf)
-	writeRecord(bw, q, includeApp)
+	writeRecord(bw, q, includeApp, nil)
 	bw.Flush()
 	return buf.String()
 }