[packer] Fix tests

[passy]

[packer] Fix tests

Summary:

Tests broke recently: https://github.com/facebook/flipper/actions/runs/8943237349/job/24567505699

Test Plan:

$ cargo test
running 4 tests
Computing manifest      ▕████████████████████▏
test test::test_included_packlist_parses ... ok
test tarsum::test::test_nested_archive_tarsum ... ok
test tarsum::test::test_differently_ordered_archives ... ok
Computing manifest      ▕████████████████████▏
test test::test_manifest ... ok

test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.01s

[facebook-github-bot]

@passy has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@passy merged this pull request in facebook/flipper@958638c956727b0d7f95589092bdbcc2d9bc50c4.