Fix release tests workflow

[jbreue16]

the cd workflow does not work properly, see https://github.com/cadet/CADET-Core/actions/runs/12296219136, even though the only difference to the CI workflow is that cadet-core is only build on linux and a different test flag is specified for the testrunner.

Maybe we dont even need a different workflow but can add the test flag to the ci workflow, with [CI] as default?

[schmoelder]

Could this be the issue: actions/checkout#1326 (comment)

[jbreue16]

Could this be the issue: actions/checkout#1326 (comment)

Why would it work then for the CI workflow?

[schmoelder]

No idea... maybe because it's triggered differently?

I was just confused by the error message:

The process '/usr/bin/git' failed with exit code 1

and started googling.