CI: Some tests are killed on Github Actions with error 137

[dfsp-spirit]

Here is an example from our GH Action runs. The reason is most likely an out-of-memory issue, though our mem use should not be that high for the prediction tests(?).

Others have run into this as well, e.g., here.

Maybe we can investigate memory usage on the CI system during the test run somehow to find out more.

[dfsp-spirit]

For now I will disable the failing tests on GitHub, so that the other tests do at least run. All tests work locally and can be run on the dev machines (and I run them often), so this should be okay for now.

Of course, this means that the coverage reported from the CI system will be way off (too low), as the tests which are not run on CI cannot be counted for coverage.