Upgrade Java version from 11 to 21 in workflow

[mwilman]

Checklist

• Issue number for this PR: Angular v21 support #3678
• Docs included?: No, not needed
• Test units included?: No, not needed
• In a clean directory, yarn install, yarn test run successfully? yes

Description

Updating CI Pipeline because of new firebase-tools. In response to https://github.com/angular/angularfire/actions/runs/20904324892

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