Run cyhy-domainsync service with --no-owned flag

[dav3r]

🗣 Description

This PR updates the run-cyhy-domainsync.service file to run cyhy-domainsync with the recently-added --no-owned flag.

💭 Motivation and context

The --no-owned flag skips resolved IP addresses that are owned by a CyHy entity other than the default owner.

See cisagov/cyhy-core#128 for more info.

🧪 Testing

Visual inspection.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• All new and existing tests pass.
• Bump major, minor, patch, pre-release, and/or build versions as appropriate via the bump_version script if this repository is versioned and the changes in this PR warrant a version bump.

✅ Pre-merge checklist

• Finalize version.

✅ Post-merge checklist

• Create a release (necessary if and only if the version was bumped).

[Copilot]

Pull Request Overview

This PR updates the systemd service file to run the cyhy-domainsync command with the --no-owned flag, which filters out IP addresses owned by non-default CyHy entities during hostname housekeeping operations.

• Added --no-owned flag to the cyhy-domainsync command execution
• Added inline documentation explaining the purpose of the flag

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[jsf9k]

Please see my two comments.