t1405: mark test that checks existence as REFFILES

The reftable backend doesn't support mere existence of reflogs.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1405-main-ref-store.sh

@@ -111,7 +111,7 @@ test_expect_success 'delete_reflog(HEAD)' '
 	test_must_fail git reflog exists HEAD
 '
 
-test_expect_success 'create-reflog(HEAD)' '
+test_expect_success REFFILES 'create-reflog(HEAD)' '
 	$RUN create-reflog HEAD &&
 	git reflog exists HEAD
 '