Update pyarrow requirement in /bindings/python

Updates the requirements on [pyarrow](https://github.com/apache/arrow) to permit the latest version.
- [Release notes](https://github.com/apache/arrow/releases)
- [Commits](apache/arrow@apache-arrow-20.0.0...apache-arrow-21.0.0)

---
updated-dependencies:
- dependency-name: pyarrow
  dependency-version: 21.0.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

bindings/python/pyproject.toml

@@ -6,7 +6,7 @@ requires = [
     # Needed for numpy headers.
     "numpy>=2.0",
     # Must be kept in sync with "project.dependencies" below.
-    "pyarrow>=20.0,<20.1.0",
+    "pyarrow>=20.0,<21.1.0",
 ]
 
 [project]