t5512: stop referring to "v1" protocol

t5512: stop referring to "v1" protocol

There really isn't a "v1" Git protocol. It's just v0 with an extra probe
which we used to test compatibility in preparation for v2. Any tests
that are looking for before/after behavior for v2 really care about
"v0". Mentioning "v1" in these tests is just making things more
confusing, because we don't care about that probe; we're really testing
v0. So let's say so.

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