use random port for test:webworker

[rluvaton]

Purpose (TL;DR) - mandatory

Dev machine may already have port 8080 taken, which will fail the test, so listening to a random port instead

How to verify - mandatory

1. Check out this branch
2. npm install
3. npm test

Checklist for author

• [x] npm run lint passes
• [x] References to standard library functions are cached.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (1eb070a) 96.05% compared to head (bb317a2) 96.05%.

:exclamation: Current head bb317a2 differs from pull request most recent head a59bb6e. Consider uploading reports for the commit a59bb6e to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2568 +/- ## ======================================= Coverage 96.05% 96.05% ======================================= Files 41 41 Lines 1928 1928 ======================================= Hits 1852 1852 Misses 76 76 ``` | [Flag](https://app.codecov.io/gh/sinonjs/sinon/pull/2568/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sinonjs) | Coverage Δ | | |---|---|---| | [unit](https://app.codecov.io/gh/sinonjs/sinon/pull/2568/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sinonjs) | `96.05% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sinonjs#carryforward-flags-in-the-pull-request-comment) to find out more.

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