Update readme for geospatial crate (#9124)

# Which issue does this PR close?

- Closes #8373.

# Rationale for this change

After #8943, columns with the extension type "geoarrow.wkb" are written
as `Geometry` or `Geography` (depending on extension type metadata) when
the `parquet` crate is built with the `geospatial` feature.

I don't beleive there are any more implementation details we need to
encapsulate in the `parquet-geospatial` crate to consider it
"implemented" (although there may be more future utilities for which
parquet-geospatial is a good home).

# What changes are included in this PR?

There is no need to duplicate the description in the issue here but it
is sometimes worth providing a summary of the individual changes in this
PR.

# Are these changes tested?

Documentation only!

# Are there any user-facing changes?

No!

Author: paleolimbot

parquet-geospatial/README.md

@@ -17,27 +17,21 @@
   under the License.
 -->
 
-# Apache Parquet Geometry/Geography Rust Implementation
+# Apache Parquet Geometry/Geography Rust Implementation Details
 
 [![crates.io](https://img.shields.io/crates/v/parquet-geospatial.svg)](https://crates.io/crates/parquet-geospatial)
 [![docs.rs](https://img.shields.io/docsrs/parquet-geospatial.svg)](https://docs.rs/parquet/latest/parquet-geospatial/)
 
-This crate contains an implementation of [Geometry and Geography Encoding] from
-[Apache Parquet]. This software is developed as part of the [Apache Arrow] project.
+This crate contains implementation details for the [Geometry and Geography Encoding] from
+[Apache Parquet], including utilities for calculating geospatial column statistics and writing
+tests. This software is developed as part of the [Apache Arrow] project.
 
 [Geometry and Geography Encoding]: https://github.com/apache/parquet-format/blob/master/Geospatial.md
 [Apache Parquet]: https://parquet.apache.org/
 [Apache Arrow]: https://arrow.apache.org/
 
 Please see the [API documentation](https://docs.rs/parquet-geospatial/latest) for more details.
 
-## 🚧 Work In Progress
-
-NOTE: This crate is under active development and is not yet ready for production use.
-If you are interested in helping, you can find more information on the GitHub [Geometry issue]
-
-[Geometry issue]: https://github.com/apache/arrow-rs/issues/8373
-
 ## License
 
 Licensed under the Apache License, Version 2.0: <http://www.apache.org/licenses/LICENSE-2.0>.