Upgrade actions/setup-java to v6

[brunoborges]

Upgrade the build workflow from actions/setup-java@v4 to @v6, preserving the repository semantic version pin style.

Validation: verified no older actions/setup-java references remain in active workflow YAML and ran git diff --check.

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[brunoborges]

my apologies for this PR. It was only supposed to hit a set of repos with a specific dependabot configuration that would prevent getting the alert of this new release