test(client-presence): cleanup type test generation

[jason-ha]

• use root entrypoint (empty string - there isn't public versus beta, etc. here)
• remove dead script entry

[github-actions]

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Based on the diff (5 lines, 1 files), I've queued these reviewers:

• Correctness — logic errors, race conditions, lifecycle issues
• Security — vulnerabilities, secret exposure, injection
• API Compatibility — breaking changes, release tags, type design
• Performance — algorithmic regressions, memory leaks
• Testing — coverage gaps, hollow tests

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[Copilot]

Pull request overview

This PR streamlines type test generation configuration for @fluid-internal/presence-definitions by aligning it with the root entrypoint behavior supported by flub generate typetests and removing an unused script variant.

Changes:

• Removed the unused typetests:gen-disabled script entry.
• Updated typeValidation.entrypoint to "" to explicitly target the package’s default/root entrypoint.