[SPARK-52680][INFRA] Remove Python 3.9 GitHub Action CI

### What changes were proposed in this pull request?

This PR aims to remove Python 3.9 GitHub Action CI for `Apache Spark 4.1.0.`
- https://github.com/apache/spark/actions/workflows/build_python_3.9.yml

This PR doesn't aim to delete Python 3.9 infra image because it can be used by `branch-4.0`.

### Why are the changes needed?

Python 3.9 will reach the end of support on October.
- https://devguide.python.org/versions/#supported-versions

We are moving the minimum requirements to Python 3.10 already.
- #51259

### Does this PR introduce _any_ user-facing change?

No, this is an infra change.

### How was this patch tested?

Manual review because this is a removal of test coverage.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #51371 from dongjoon-hyun/SPARK-52680.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: dongjoon-hyun

.github/workflows/build_python_3.9.yml

@@ -36,7 +36,6 @@ This README file only contains basic setup instructions.
 |            | [![GitHub Actions Build](https://github.com/apache/spark/actions/workflows/build_maven_java21_arm.yml/badge.svg)](https://github.com/apache/spark/actions/workflows/build_maven_java21_arm.yml)                 |
 |            | [![GitHub Actions Build](https://github.com/apache/spark/actions/workflows/build_coverage.yml/badge.svg)](https://github.com/apache/spark/actions/workflows/build_coverage.yml)                          |
 |            | [![GitHub Actions Build](https://github.com/apache/spark/actions/workflows/build_python_pypy3.10.yml/badge.svg)](https://github.com/apache/spark/actions/workflows/build_python_pypy3.10.yml)                   |
-|            | [![GitHub Actions Build](https://github.com/apache/spark/actions/workflows/build_python_3.9.yml/badge.svg)](https://github.com/apache/spark/actions/workflows/build_python_3.9.yml)                             |
 |            | [![GitHub Actions Build](https://github.com/apache/spark/actions/workflows/build_python_3.10.yml/badge.svg)](https://github.com/apache/spark/actions/workflows/build_python_3.10.yml)                           |
 |            | [![GitHub Actions Build](https://github.com/apache/spark/actions/workflows/build_python_3.11_classic_only.yml/badge.svg)](https://github.com/apache/spark/actions/workflows/build_python_3.11_classic_only.yml) |
 |            | [![GitHub Actions Build](https://github.com/apache/spark/actions/workflows/build_python_3.11_arm.yml/badge.svg)](https://github.com/apache/spark/actions/workflows/build_python_3.11_arm.yml)                   |