fsck: use local repository

fsck: use local repository

In 0d30feef3c5 (fsck: create scaffolding for rev-index checks,
2023-04-17) and later 5a6072f631d (fsck: validate .rev file header,
2023-04-17), the check_pack_rev_indexes() method was created with a
'struct repository *r' parameter. However, this parameter was unused and
instead 'the_repository' was used in its place.

Fix this situation with the obvious replacement.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>