[chg] deactivate new installer

GitHub Issue: python-poetry/poetry#3199

.gitlab-ci.yml

@@ -51,6 +51,7 @@ stages:
   # TODO: restore some backend
   # Install poetry
   pip3 install poetry
+  poetry config experimental.new-installer false
   poetry install 
   poetry run opsiconfd --setup --log-level-stderr=5
   # Create adminuser used with opsiconfd-perftest.py