Fix for polars 1.33.0 (dtype becoming mandatory)

[charles-turner-1]

Change Summary

• Specifies that iterable columns are decoded to the polars dtype pl.List[pl.Utf8] when opening catalogs with polars. (see https://docs.pola.rs/api/python/dev/reference/expressions/api/polars.Expr.str.json_decode.html)
• Update the ci/environment.yml to use polars>=1.33.0

Related issue number

N/A

Checklist

• Unit tests for the changes exist
• Tests pass on CI
• Documentation reflects the changes where applicable

[charles-turner-1]

I'm gonna leave this one for now: see #744.

I'll take some time to dig into that and see I can figure out that issue first, as it pins to polars <=1.33.

Seems some weird (and breaking 😞) changes came along for the ride with that release, so I think pinning a max version of polars per release is going to be sensible going forwards.