t5531: further "matching" fixups

Commit 43eb920 switched one of the sub-repository in this test to matching to prepare for a world where the default becomes "simple". However, the main repository needs a similar change. We did not notice any test failure when merged with b2ed944 (push: switch default from "matching" to "simple", 2013-01-04) because t5531.6 is trying to provoke a failure of "git push" due to a submodule check. When combined with b2ed944 the push still fails, but for the wrong reason (because our upstream setup does not exist, not because of the submodule). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>