RayDataExecutionOptions writes deprecated ctx.use_polars

[geoHeil]

src/dagster_ray/configs.py:100 writes ctx.use_polars = self.use_polars. Ray 2.55 warns on that setter and proxies to use_polars_sort; every apply() / apply_remote() emits a DeprecationWarning from ray.data.context.

Fix: rename the field and setattr target to use_polars_sort. If backward-compat matters, keep use_polars as a deprecated alias on RayDataExecutionOptions that forwards to use_polars_sort.