chore(rust/sedona-geoparquet): Fix clippy errors

[paleolimbot]

On main we have several clippy errors:

Checking sedona-geoparquet v0.3.0 (/home/runner/work/sedona-db/sedona-db/rust/sedona-geoparquet)
error: called `unwrap` on `item.value` after checking its variant with `is_some`
   --> rust/sedona-geoparquet/src/format.rs:210:57
    |
208 |                     if item.key == "geo" && item.value.is_some() {
    |                                             -------------------- the check is happening here
209 |                         let this_geoparquet_metadata =
210 |                             GeoParquetMetadata::try_new(item.value.as_ref().unwrap())?;
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: try using `match`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.93.0/index.html#unnecessary_unwrap
    = note: `-D clippy::unnecessary-unwrap` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_unwrap)]`

error: called `unwrap` on `item.value` after checking its variant with `is_some`
   --> rust/sedona-geoparquet/src/metadata.rs:389:50
    |
388 |                 if item.key == "geo" && item.value.is_some() {
    |                                         -------------------- the check is happening here
389 |                     return Ok(Some(Self::try_new(item.value.as_ref().unwrap())?));
    |                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: try using `match`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.93.0/index.html#unnecessary_unwrap

error: could not compile `sedona-geoparquet` (lib) due to 2 previous errors

This PR fixes them!