v2021 ← v2022dev2: ci-buildpackage: Avoid git-restore as it is too new

Backport of !203 (merged)

Use of git restore has been introduced in commit e954d2be "ci-buildpackage: use wrap-and-sort as a workaround for odd packages".

It works on the Bullseye-based v2022dev2, but on older Buster-based release git restore is not available.

Replace it with the old-style git checkout.