Update pola-rs and remove workaround

[sourcefrog]

trying to fix CI failures like in https://github.com/duckdb/duckdb-rs/actions/runs/12446619688

[mbp-stripe]

It looks like there is some other additional CI breakage, maybe version skew with arrow2:

   Compiling duckdb v1.1.1 (D:\a\duckdb-rs\duckdb-rs\crates\duckdb)
error[E0609]: no field `data_type` on type `ArrowField`
Error:    --> crates\duckdb\src\raw_statement.rs:178:103
    |
178 |             let import_arrow2_array = arrow2::ffi::import_array_from_c(ffi_arrow2_array, arrow2_field.data_type);
    |                                                                                                       ^^^^^^^^^ unknown field
    |
    = note: available fields are: `name`, `dtype`, `is_nullable`, `metadata`

For more information about this error, try `rustc --explain E0609`.
error: could not compile `duckdb` (lib) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
Error: Process completed with exit code 1.