Update Trusty PR evaluator/ruletype documentation

[puerco]

Summary

This PR updates the documentation of the trusty rule to match the last changes to the evaluator.

Change Type

Mark the type of change your PR introduces:

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

N/A

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 51.964% (-0.02%) from 51.98%
when pulling b5bfccd on puerco:trusty-docs
into 586144c on stacklok:main.