[BUG] Unreleased OpenSearch integration tests are failing to build an instance

[kimpepper]

What is the bug?

The Integration with Unreleased OpenSearch / test (main, 11, 17) test is failing in what looks like an unrelated issue:

Starting a Gradle Daemon (subsequent builds will be faster)

FAILURE: Build failed with an exception.

* Where:
Build file '/home/runner/work/opensearch-php/opensearch-php/opensearch/buildSrc/build.gradle' line: 78

* What went wrong:
A problem occurred evaluating project ':buildSrc'.
> At least Java 21 is required to build opensearch gradle tools

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What is the expected behavior?

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What is your host/environment?

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[kimpepper]

Might be worth adding a workflow_dispatch trigger to that workflow so we can manually test on main.

[kimpepper]

#267 fixes this