Switch to artifacts v4

[PietrH]

camtraptor/.github/workflows/test-coverage.yaml

Line 52 in 079713f

uses: actions/upload-artifact@v3

See https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

Starting December 5, 2024, GitHub Actions customers will no longer be able to use v3 of actions/upload-artifact or actions/download-artifact. Customers should update workflows to begin using v4 of the artifact actions as soon as possible. While v4 of the artifact actions improves upload and download speeds by up to 98% and includes several new features, there are key differences from previous versions that may require updates to your workflows. Please see the documentation in the project repositories for guidance on how to migrate your workflows.

Artifacts within github actions (= cache, reusing data over github actions runs) are moving to a higher version, we need to switch over before the 5th of december. This is a single letter change.