Drone CI is not reachable anymore -> No instrumentation testing

[PhilLab]

Since around a week, https://drone.nextcloud.com/ and thus our integration tests are not executed anymore.

Have we stopped using Drone or is it "just" down?

[PhilLab]

@alperozturk96 seems to be up again, right? Feel free to close if nothing else to do here. Out of curiosity: what happened?