GEODE-10670: Pin gradle/actions/setup-gradle to an approved SHA on su…

[JinwooHwang]

Pin gradle/actions/setup-gradle to an approved SHA on support/1.15

For all changes, please confirm:

• Is there a JIRA ticket associated with this PR? Is it referenced in the commit message?
• Has your PR been rebased against the latest commit within the target branch (typically develop)?
• Is your initial contribution a single, squashed commit?
• Does gradlew build run cleanly?
• Have you written or updated unit tests to verify your changes?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?