build(deps): bump polars from 1.20.0 to 1.21.0

Bumps [polars](https://github.com/pola-rs/polars) from 1.20.0 to 1.21.0.
- [Release notes](https://github.com/pola-rs/polars/releases)
- [Commits](pola-rs/polars@py-1.20.0...py-1.21.0)

---
updated-dependencies:
- dependency-name: polars
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]