bump unity-builder action version example block

[eronnen]

bump unity-builder action version in sshPublicKeysDirectoryPath example block

Checklist

• [ ] Read the contribution guide and accept the code of conduct
• [ ] Readme (updated or not needed)
• [ ] Tests (added, updated or not needed)

[webbertakken]

https://github.com/game-ci/unity-builder/actions/runs/6102692741

This is the workflow that will automatically update the v3 tag, once the workflow run is assigned a runner.

[github-actions[bot]]