[Schema] Fix: correct Resource type hints in ListResourcesResult

[CodeWithKyrian]

This PR corrects the PHPDoc type hints in ListResourcesResult to use proper types instead of PHP's built-in resource type.

Motivation and Context

The @param and @return annotations were using lowercase resource, which PHPStan interprets as PHP's built-in type for external resources (like file handles), not the SDK's Resource class.

[chr-hertel]

Thanks @CodeWithKyrian