t5550: put auth-required repo in auth/dumb

t5550: put auth-required repo in auth/dumb

In most of our tests, we put repos to be accessed by dumb
protocols in /dumb, and repos to be accessed by smart
protocols in /smart.  In our test apache setup, the whole
/auth hierarchy requires authentication. However, we don't
bother to split it by smart and dumb here because we are not
currently testing smart-http authentication at all.

That will change in future patches, so let's be explicit
that we are interested in testing dumb access here. This
also happens to match what t5540 does for the push tests.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>