Update Jersey holidays

[PPsyrius]

Proposed change

This PR adds Jul 15, 2024, as a public Holiday for Jersey as outlined in [1] [2].

Other Public holiday names are also changed to better match the actual usage in Jersey 🇯🇪 rather than the United Kingdom 🇬🇧 . i.e. %s (observed) is changed to %s (substitute day), Late Summer Public Holiday is simply called Summer Public Holiday, May Day is called Early May Bank Holiday (except in 2024 which is instead called May Bank Holiday)

Type of change

• [ ] New country/market holidays support (thank you!)
• [x] Supported country/market holidays update (calendar discrepancy fix, localization)
• [ ] Existing code/documentation/test/process quality improvement (best practice, cleanup, refactoring, optimization)
• [ ] Dependency update (version deprecation/pin/upgrade)
• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] Breaking change (a code change causing existing functionality to break)
• [ ] New feature (new python-holidays functionality in general)

Checklist

• [x] I've followed the contributing guidelines
• [x] I've run make pre-commit, it didn't generate any changes
• [x] I've run make test, all tests passed locally

[codecov[bot]]

Codecov Report

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

Project coverage is 100.00%. Comparing base (44dd050) to head (42d9062). Report is 5 commits behind head on dev.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #1971 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 188 188 Lines 11403 11403 Branches 1789 1789 ========================================= Hits 11403 11403 ```

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