[SPARK-53925][INFRA] Use MacOS 26 in build_maven_java21_macos15.yml

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to upgrade MacOS from 15 to 26 in build_maven_java21_macos15.yml.

Why are the changes needed?

To use the latest MacOS as a part of Apache Spark 4.1.0 preparation.

• https://github.com/actions/runner-images/blob/main/images/macos/macos-26-arm64-Readme.md

Does this PR introduce any user-facing change?

No, this is an infra-only change.

How was this patch tested?

Manual review.

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

No.

[dongjoon-hyun]

Could you review this PR when you have some time, @sarutak ?

[sarutak]

LGTM.
Should we change python_hosted_runner_test.yml as well?
But it's ok to do in a separate PR.

spark/.github/workflows/python_hosted_runner_test.yml

Line 47 in fcd8371

default: macos-15

[dongjoon-hyun]

Thank you. Yes, I want to stabilize this first because Python is more complex.

[dongjoon-hyun]

Let me merge this because this is irrelevant to the CI result. I'll trigger manually after merging.

[dongjoon-hyun]

For the record, this is verified here.

• https://github.com/apache/spark/actions/workflows/build_maven_java21_macos26.yml
  • https://github.com/apache/spark/actions/runs/18541419063/job/52849613995