TST: slow test_nearest_upsample_with_limit with tzlocal
Doing `pytest pandas/tests --skip-slow --durations=10` the top two entries are

```
71.76s call     pandas/tests/resample/test_datetime_index.py::test_nearest_upsample_with_limit[tzlocal()-30S-Y]
59.86s call     pandas/tests/resample/test_datetime_index.py::test_nearest_upsample_with_limit[tzlocal()-30S-10M]
```

Because this uses the tz_aware_fixture, there isn't a trivial way to add a pytest.mark.slow to this, but figuring something out may be worthwhile.