Remove starter-library/ (#48478)

- @noahtalerman: New Fleet instances now use the `fleetctl new`
templates: https://github.com/fleetdm/fleet/pull/42768/changes
- This starter library was only used for new Fleet instances and as of
the changes above is no longer used


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## Summary by CodeRabbit

* **Chores**
* Cleaned up the starter library configuration by removing two
preconfigured team entries from the example setup.

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Author: noahtalerman