Do not drop seam-crossing faces in polygon plots

`plot.polygons()` currently excludes faces crossing the longitude seam by default.

Reproducer:

```python
uxds = ux.open_dataset(
    "test/meshfiles/scrip/ne30pg2/grid.nc",
    "20250904.v3.LR.historical_0101.EM_CMIP7.chrysalis.eam.h0.2014-12.nc",
)
uxds["U"].isel(time=0, lev=0).plot.polygons()
```

The data has no NaNs, but 120 ne30pg2 seam-crossing faces are dropped and show as white blocks.