package.loader: Fix type warning with swh.core > 0.2.0
The next version of swh.core will allow mypy to detect the return type of origin_visit_add is Iterable.
Migrated from D3655 (view on Phabricator)
The next version of swh.core will allow mypy to detect the return type of origin_visit_add is Iterable.
Migrated from D3655 (view on Phabricator)