fix: remove test-report.yml build pipeline (#444)

Remove the
[`test-report.yml`](https://github.com/Testably/Testably.Abstractions/actions/workflows/test-report.yml)
build pipeline as it is no longer compatible with
[`actions/upload-artifact
v4`](https://github.com/actions/upload-artifact?tab=readme-ov-file#v4---whats-new).

Author: vbreuss