test_IteratorWithAggregation is flaky on Windows across pythons

only this month:

```
dandi@drogon:/mnt/backup/dandi/tinuous-logs/dandi-cli/2024/09$ git grep '::test_IteratorWithAggregation.*FAIL' | grep '/test '
06/github/pr/1496/1aa3df8/Tests/5808/test (windows-2019, 3.8, normal)/8_Run all tests.txt:2024-09-06T01:32:43.4846312Z dandi/support/tests/test_iterators.py::test_IteratorWithAggregation FAILED
13/github/pr/1497/7ed9c30/Tests/5822/test (windows-2019, 3.8, normal)/8_Run all tests.txt:2024-09-13T00:41:01.9741446Z dandi/support/tests/test_iterators.py::test_IteratorWithAggregation FAILED
13/github/pr/1497/8dba010/Tests/5824/test (windows-2019, 3.10, normal)/8_Run all tests.txt:2024-09-13T14:09:28.7882442Z dandi/support/tests/test_iterators.py::test_IteratorWithAggregation FAILED
13/github/pr/1499/f78350f/Tests/5826/test (windows-2019, 3.9, normal)/8_Run all tests.txt:2024-09-13T15:33:14.3137703Z dandi/support/tests/test_iterators.py::test_IteratorWithAggregation FAILED
20/github/pr/1499/8d739b7/Tests/5841/test (windows-2019, 3.10, normal)/8_Run all tests.txt:2024-09-20T19:00:41.9257891Z dandi/support/tests/test_iterators.py::test_IteratorWithAggregation FAILED
```

with another fresh in
- https://github.com/dandi/dandi-cli/pull/1499

```
________________________ test_IteratorWithAggregation _________________________
dandi\support\tests\test_iterators.py:72: in test_IteratorWithAggregation
assert got in ([], [0])
E assert [0, 1] in ([], [0])
```

I for now will mark it as xfail