[Refactor] Use uniq helper in session scopes

[gonzaloriestra]

What is being refactored?

This PR refactors packages/cli-kit/src/private/node/session/scopes.ts to use the uniq helper from @shopify/cli-kit/common/array instead of manual Set deduplication.

Why is this necessary?

Using the uniq utility function throughout the codebase improves consistency and makes the intent of array deduplication clearer compared to the manual Array.from(new Set(array)) pattern.

How to test your changes?

CI

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PR created automatically by Jules for task 9575244148370966177 started by @gonzaloriestra

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