chore(ci): remove superfluous 'Install Oras' step

[BethGriggs]

Description of the change

Removes superfluous 'Install Oras' step - according to https://github.com/actions/runner-images/blob/main/images/ubuntu/Ubuntu2204-Readme.md#cli-tools this is bundled by default in all Ubuntu GitHub Actions runners.

Also cited in oras-project/setup-oras#17

Existing or Associated Issue(s)

This is in effort to mitigate the following warning - we may as well use the bundled version so we pick up updates when GitHub applies them:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: oras-project/setup-oras@ee7dbe1. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

Additional Information

Checklist

• Chart version bumped in Chart.yaml according to semver.
• Variables are documented in the values.yaml and added to the README.md. The pre-commit utility can be used to generate the necessary content. Use pre-commit run -a to apply changes.
• JSON Schema template updated and re-generated the raw schema via pre-commit hook.
• List tests pass for Chart using the Chart Testing tool and the ct lint command.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[BethGriggs]

Never mind, fake news. It's being removed in Ubuntu 24.04 runners for maintenance reasons - actions/runner-images#9848