The three BackfillEnqueueWorkerTest cases were timing out because the
default types list includes :era5, which cascades through inline Oban
into Era5Client.poll_and_download where Process.sleep blocks for the
full 60s test timeout. Era5Client uses bare Req.get with no plug hook,
so it can't be stubbed via Req.Test the way the other clients are. Pass
explicit non-ERA5 types in the three affected cases — ERA5 has its own
coverage and these tests don't assert anything era5-specific.
Also replace two `length(results) > 0` checks in asos_nudge_test with
`results != []` to silence credo warnings.
