CONFIG: Use Xcode 15.4 for GitHub workflows

[codecov[bot]]

Codecov Report

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

Project coverage is 89.15%. Comparing base (5968076) to head (a098377). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #182 +/- ## ======================================= Coverage 89.15% 89.15% ======================================= Files 198 198 Lines 2721 2721 ======================================= Hits 2426 2426 Misses 295 295 ```

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