Update task D5 in the Git lab to account for that the old scala runner has been replaced by scala-cli

[EliasAAradsson]

This update may be done in one of two ways as I see it. Either using the new scala runner (scala-cli), or by finding a way to run .class files manually compiled with scalac with the new scala runner or by other means. The first way is a simpler fix. The second way I'm not sure about how to do, but it has the advantage of making it easy to see the .gitignore in action.