Update gradle/gradle-build-action digest to 87a9a15

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gradle/gradle-build-action	action	digest	842c587 -> 87a9a15

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Configuration

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🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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