t0410: convert tests to use DEFAULT_REPO_FORMAT prereq

t0410: convert tests to use DEFAULT_REPO_FORMAT prereq

In t0410 we have two tests which exercise how partial clones behave in
the context of a repository with extensions. These tests are marked to
require a repository using SHA1 and the "files" backend because we
explicitly set the repository format version to 0, and setting up either
the "objectFormat" or "refStorage" extensions requires a repository
format version of 1.

We have recently introduced a new DEFAULT_REPO_FORMAT prerequisite.
Despite capturing the intent more directly, it also has the added
benefit that it can easily be extended in the future in case we add new
repository extensions. Adapt the tests to use it.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>