🧪 [test] add unit tests for expectArray

[akutuva21]

🎯 What: This PR adds missing unit tests for the expectArray function in scripts/validate-metadata.js.
📊 Coverage: The tests cover the happy path (valid arrays do not append to the errors list) and error conditions (strings, null, objects, and undefined correctly append an error message with the label and filepath to the errors list).
✨ Result: Enhanced test coverage and reliability for metadata validation logic.

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PR created automatically by Jules for task 12870449047627298925 started by @akutuva21

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