Upgrade codecov-action to v4

[johannaengland]

CODECOV_TOKEN is also in the repository secrets.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[github-actions[bot]]

Test results

    3 files      3 suites   41s :stopwatch:   63 tests   63 :heavy_check_mark: 0 :zzz: 0 :x: 189 runs  189 :heavy_check_mark: 0 :zzz: 0 :x:

Results for commit fe8163ef.

[codecov[bot]]

Codecov Report

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

Project coverage is 71.01%. Comparing base (5c9469f) to head (fe8163e). Report is 12 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #57 +/- ## ========================================== - Coverage 71.60% 71.01% -0.60% ========================================== Files 13 13 Lines 1363 1380 +17 ========================================== + Hits 976 980 +4 - Misses 387 400 +13 ```

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