t5704: send object-format capability with SHA-256

t5704: send object-format capability with SHA-256

When we speak protocol v2 in this test, we must pass the object-format
header if the algorithm is not SHA-1.  Otherwise, git upload-pack fails
because the hash algorithm doesn't match and not because we've failed to
speak the protocol correctly.  Pass the header so that our assertions
test what we're really interested in.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>