Delete 4 unused model files

converts 3 model files and .gitlab-ci.yml from dos format to unix format, latter is preferred by git and most programs regarding this repo AFAIK

Now just deletes those 3 model files + one of their duplicates. .gitlab-ci.yml is converted to UNIX format by !1150 (merged) already.

Draft until models/keyhunt/key.obj has been moved to mediasource repository.