chore: Adjust Playwright CI retries (#2639)

## Summary

- Remove the custom Playwright worker limit calculation so Playwright
can choose the worker count itself.
- Increase CI retries from 4 to 20.

## Validation

- Not run per request to submit the PR directly. Earlier
formatting/check commands could not complete because the sandbox could
not resolve npm registry packages.

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## Summary by CodeRabbit

* **Chores**
* Simplified Playwright test worker configuration to use default
settings across all environments instead of dynamic allocation.
* Increased CI test retry attempts from 4 to 20 to improve overall test
reliability and reduce flaky test failures in continuous integration.

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