Ensure the systemd-timesyncd service is not masked

[rmol]

Status

Ready for review

Description of Changes

Explicitly unmasks the systemd-timesyncd service.

Fixes #5840.

Testing

• Build a Focal staging environment, or install on hardware.
• On both servers:
  • Ensure that systemctl list-unit-files --state=masked | grep time reports nothing.
  • systemctl list-unit-files systemd-timesyncd.service should report that the service is enabled.
  • systemctl status systemd-timesyncd should report that it is enabled and loaded.

Deployment

No new concerns.

Checklist

If you made changes to the server application code:

• Linting (make lint) and tests (make test) pass in the development container

If you made changes to the system configuration:

• Configuration tests pass

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

Choose one of the following:

• I have opened a PR in the docs repo for these changes, or will do so later
• I would appreciate help with the documentation
• These changes do not require documentation

[conorsch]

Looks good, fine to merge when CI passes.