test: Pick another port on `PermissionDenied`

[larseggert]

Receiving which indicates that we randomly picked a privileged port. This happens esp. on Windows, even with ports > 1024.

Broken out of #23

[codecov[bot]]

Codecov Report

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

Project coverage is 92.62%. Comparing base (d2d7da5) to head (0467cf7). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #24 +/- ## ======================================= Coverage 92.62% 92.62% ======================================= Files 1 1 Lines 244 244 ======================================= Hits 226 226 Misses 18 18 ```

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