update .gitlab-ci.yml

1 job for adi-dev in 19 seconds (queued for 3 seconds)
Name Stage Failure
failed
TestJobLinux Linux
$ git clone git@github.com:MontiCore/EmbeddedMontiArc/tree/master/generators/EMAM2Cpp.git
Cloning into 'EMAM2Cpp'...
Host key verification failed.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
Cleaning up file based variables
ERROR: Job failed: exit code 1