[SPARK-56852] Upgrade Gradle to 9.5.1

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR upgrades Gradle to 9.5.1.

Why are the changes needed?

To bring the latest Gradle bug fixes:

• https://docs.gradle.org/9.5.1/release-notes.html (2026-05-12)

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Pass the CIs and check the log.

Welcome to Gradle 9.5.1!
Here are the highlights of this release:
 - Task provenance in reports and failure messages
 - Type-safe accessors for precompiled Kotlin Settings plugins
For more details see https://docs.gradle.org/9.5.1/release-notes.html

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

Generated-by: Claude Code (Claude Opus 4.7)

[dongjoon-hyun]

Thank you, @peter-toth .

[dongjoon-hyun]

Thank you, @viirya .

[dongjoon-hyun]

Merged to main