[Docs][Rust] Mark Avro external data format status as R/W for Rust

[jecsand838]

Describe the enhancement requested

Summary

The Third‑Party Data Formats Implementation Status table currently leaves the Rust cell blank for Avro. With the competition of apache/arrow-rs#4886 and the introduction of the official arrow-avro crate in arrow-rs, this row should list Rust = R/W.

• Affected page: https://arrow.apache.org/docs/status.html#third-party-data-formats
• Current docs version shown on the page: v21.0.0

Evidence

• Release notes: arrow-rs 57.0.0 (2025‑10‑19) lists “Added Avro support (new arrow-avro crate)”.
  https://github.com/apache/arrow-rs/releases/tag/57.0.0

• Official rust docs (arrow.apache.org): arrow-avro crate provides a reader and a writer
  https://arrow.apache.org/rust/arrow_avro/index.html

• docs.rs for arrow-avro 57.0.0 says the same (reader + writer), with runnable round‑trip examples.
  https://docs.rs/arrow-avro/latest/arrow_avro/

• Current status page shows Avro with R for C++ and Java, but Rust is blank, implying no support.
  https://arrow.apache.org/docs/status.html#third-party-data-formats

Proposed change

Edit docs/source/status.rst (the “Third‑Party Data Formats” table) and set Rust's Avro cell to R/W.

Component(s)

Documentation

[alamb]

Closed in #47930 / 7623887

I fear I forgot to use the close script -- sorry about that