Update CI failure note to include a link to DEVELOPER_GUIDE

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Is your feature request related to a problem? Please describe.

When Gradle checks CI fails developers don't know what to do.

Describe the solution you'd like

In #4868 we have added a section to describe what to do with failed tests in CI. Can we add a link to https://github.com/opensearch-project/OpenSearch/blob/main/DEVELOPER_GUIDE.md#flakey-tests in this box?

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@peterzhuamazon Do you know where to make this change?

https://github.com/opensearch-project/OpenSearch/blob/e403799fbccee4fc14208eab0d88ace20f96f2fe/.github/workflows/gradle-check.yml