[Refactor] Simplify extractMyshopifyHandle using optional chaining

[gonzaloriestra]

WHAT is this pull request doing?

Refactored extractMyshopifyHandle in packages/cli-kit/src/public/common/url.ts to simplify control flow using optional chaining instead of an explicit null check and ternary operator.

How to test your changes?

CI

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

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PR created automatically by Jules for task 5073782902792885091 started by @gonzaloriestra

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